Formed building materials

ABSTRACT

Formed building materials comprising a sequestered CO 2  are provided. The building materials of the invention include a composition comprising a carbonate/bicarbonate component. Additional aspects of the invention include methods of making and using the formed building materials.

CROSS-REFERENCE

This application is a continuation-in-part of U.S. patent application Ser. No. 13/191,209, filed 26 Jul. 2011, which is a divisional of U.S. patent application Ser. No. 12/826,209, filed 29 Jun. 2010, now U.S. Pat. No. 8,006,446, which is a continuation of U.S. patent application Ser. No. 12/571,398, filed 30 Sep. 2009, now U.S. Pat. No. 7,771,684, which claims the benefit of U.S. Provisional Patent Application No. 61/110,489, filed 31 Oct. 2008, titled “CO₂-Sequestering Formed Building Materials”; U.S. Provisional Patent Application No. 61/149,610, filed 3 Feb. 2009, titled “CO₂-Sequestering Formed Building Materials”; U.S. Provisional Patent Application No. 61/246,042, filed 25 Sep. 2009, titled “CO₂-Sequestering Formed Building Materials”; and U.S. Provisional Patent Application No. 61/101,631, filed 30 Sep. 2008, titled “CO₂ Sequestration,” each of which applications is incorporated herein by reference in its entirety. This application further claims the benefit of U.S. Provisional Patent Application No. 61/475,204, filed 13 Apr. 2011, titled “CO₂-Sequestering Formed Building Materials,” which application is incorporated herein by reference in its entirety.

BACKGROUND

Carbon dioxide (CO₂) emissions have been identified as a major contributor to the phenomenon of global warming and ocean acidification. CO₂ is a by-product of combustion and it creates operational, economic, and environmental problems. It is expected that elevated atmospheric concentrations of CO₂ and other greenhouse gases will facilitate greater storage of heat within the atmosphere leading to enhanced surface temperatures and rapid climate change. CO₂ has also been interacting with the oceans driving down the pH toward 8.0. CO₂ monitoring has shown atmospheric CO₂ has risen from approximately 280 parts per million (ppm) in the 1950s to approximately 380 ppm today, and is expect to exceed 400 ppm in the next decade. The impact of climate change will likely be economically expensive and environmentally hazardous. Reducing potential risks of climate change will require sequestration of CO₂.

SUMMARY

Provided herein is a method for producing a drywall product, comprising: a) processing a waste gas stream comprising carbon dioxide with a process water to produce an original composition comprising carbonates, bicarbonates, or a combination of carbonates and bicarbonates; b) removing at least a portion of the process water from the original composition to produce a concentrated composition, concentrated with respect to the carbonates, bicarbonates, or the combination thereof; d) producing from the concentrated composition a drywall slurry mixture; and e) depositing the drywall slurry mixture between two sheets of backing material to form the drywall product. In some embodiments, the method further comprises evaporating residual water from the drywall product. In some embodiments, the method further comprises cutting the drywall product for commercial use. In some embodiments, removing process water from the original composition comprises removing no more process water than is needed for the drywall slurry mixture. In some embodiments, removing process water from the original composition produces a concentrated composition comprising at least 25% solids. In some embodiments, removing process water from the original composition produces a concentrated composition comprising at least 50% solids. In some embodiments, removing process water from the original composition comprises concentrating the original composition to dryness to produce a dry composition. In some embodiments, concentrating the original composition to dryness comprises drying the composition at room temperature. In some embodiments, concentrating the original composition to dryness comprises drying the composition at elevated temperature. In some embodiments, the dry composition is slurried with slurry water to produce the drywall slurry mixture. In some embodiments, the slurry water comprises recovered process water. In some embodiments, the slurry water comprises fresh water. In some embodiments, solids of the drywall slurry mixture comprises at least 50% by weight carbonates, bicarbonates, or a combination of carbonates and bicarbonates. In some embodiments, the drywall slurry mixture comprises at least 75% by weight carbonates, bicarbonates, or a combination of carbonates and bicarbonates. In some embodiments, the drywall slurry mixture comprises at least 95% by weight carbonates, bicarbonates, or a combination of carbonates and bicarbonates. In some embodiments, solids of the drywall slurry mixture comprise calcium carbonate. In some embodiments, the calcium carbonate comprise metastable calcium carbonate. In some embodiments, the metastable calcium carbonate is selected from the group consisting of amorphous calcium carbonate, vaterite, aragonite, and combinations thereof. In some embodiments, the drywall slurry mixture further comprises calcite. In some embodiments, the drywall slurry mixture further comprises calcined gypsum. In some embodiments, the method further comprises adding additives to the drywall slurry mixture, the additives selected from the group consisting of anti-desiccants, fibrous materials, accelerators, set retarders, plasticizers, foaming agents, fire resistance agents, mildew resistance agents, and combinations thereof. In some embodiments, anti-desiccants are selected from the group consisting of natural starches, acid-modified starches, or a combination thereof. In some embodiments, acid-modified starches are selected from the group consisting of corn starches, potato starches, wheat stock starches, and combinations thereof. In some embodiments, fibrous materials are selected from the group consisting of wood fibers, dry paper fibers, cellulose fibers, perlite, fiberglass fibers, and combinations thereof. In some embodiments, fibrous materials are added to the drywall slurry mixture to lower drywall product density and to increase physical properties of the drywall product. In some embodiments, accelerators are selected from the group consisting of calcium sulfate dihydrate, potassium sulfate, and a combination thereof. In some embodiments, set retarders comprise diethylene triamine pentaacetic acid (“DTPA”). In some embodiments, foaming agents are selected from the group consisting of alkyl ether sulfates, ammonium alkyl ethoxy sulfates, and a combination thereof. In some embodiments, foaming agents are added to the drywall slurry mixture to lower density in the drywall product. In some embodiments, fire resistance agents are selected from the group consisting of perlite, vermiculite, boric acid, and combinations thereof. In some embodiments, the method further comprises adding recycled materials to the drywall slurry mixture, the recycled materials selected from the group consisting of fly ash, slag, cement kiln dust, and combinations thereof. In some embodiments, the two sheets of backing material comprise sheets of paper or fiberglass. In some embodiments, the sheets of backing material comprise sheets of paper. In some embodiments, at least one sheet of the two sheets of paper comprise an oil-based additive, imparting moisture resistance to the drywall product. In some embodiments, at least one sheet of the two sheets of backing material comprise a skim coat or a built-up plaster finish, imparting moisture resistance and mold resistance to the drywall product. In some embodiments, the drywall product is foil lined, imparting moisture resistance to the drywall product. In some embodiments, the drywall product is lead lined, imparting radiation resistance to the drywall product.

Provided herein is a drywall product produced in accordance with any one of the foregoing methods for producing a drywall product.

Provided herein is a drywall product comprising: a) a drywall exterior comprising two sheets of paper or fiberglass and b) a drywall interior comprising carbonates, bicarbonates, or a combination of carbonates and bicarbonates, wherein the carbonates, bicarbonates, or the combination of carbonates and bicarbonates comprise at least 50% by weight of the drywall interior, the remainder of the drywall interior comprising calcined gypsum, anti-desiccants, fibrous materials, accelerators, set retarders, plasticizers, foaming agents, fire resistance agents, mildew resistance agents, and combinations of the foregoing, and wherein the drywall interior is disposed between the two sheets of drywall exterior. In some embodiments, the drywall interior comprises at least 75% by weight carbonates, bicarbonates, or the combination of carbonates and bicarbonates comprise. In some embodiments, the drywall interior comprises at least 95% by weight carbonates, bicarbonates, or the combination of carbonates and bicarbonates comprise. In some embodiments, the drywall interior comprises at least 50% by weight carbonates. In some embodiments, the drywall interior comprises at least 75% by weight carbonates. In some embodiments, the drywall interior comprises at least 95% by weight carbonates. In some embodiments, the carbonates comprise metastable calcium carbonates. In some embodiments, the metastable calcium carbonates are selected from the group consisting of amorphous calcium carbonate, vaterite, aragonite, and combinations thereof. In some embodiments, the drywall interior further comprises calcite. In some embodiments, anti-desiccants are selected from the group consisting of natural starches, acid-modified starches, or a combination thereof. In some embodiments, acid-modified starches are selected from the group consisting of corn starches, potato starches, wheat stock starches, and combinations thereof. In some embodiments, fibrous materials are selected from the group consisting of wood fibers, dry paper fibers, cellulose fibers, perlite, fiberglass fibers, and combinations thereof. In some embodiments, fibrous materials lower drywall product density and to increase physical properties of the drywall product. In some embodiments, accelerators are selected from the group consisting of calcium sulfate dihydrate, potassium sulfate, and a combination thereof. In some embodiments, set retarders comprise diethylene triamine pentaacetic acid (“DTPA”). In some embodiments, foaming agents are selected from the group consisting of alkyl ether sulfates, ammonium alkyl ethoxy sulfates, and a combination thereof. In some embodiments, foaming agents lower density in the drywall product. In some embodiments, fire resistance agents are selected from the group consisting of perlite, vermiculite, boric acid, and combinations thereof. In some embodiments, the drywall interior further comprises recycled materials, the recycled materials selected from the group consisting of fly ash, slag, cement kiln dust, and combinations thereof. In some embodiments, the drywall exterior comprises two sheets of paper. In some embodiments, at least one sheet of the two sheets of paper comprise an oil-based additive, imparting moisture resistance to the drywall product. In some embodiments, at least one sheet of the two sheets of drywall exterior comprises a skim coat or a built-up plaster finish, imparting moisture resistance and mold resistance to the drywall product. In some embodiments, the drywall product is foil lined, imparting moisture resistance to the drywall product. In some embodiments, the drywall product is lead lined, imparting radiation resistance to the drywall product.

Provided herein is a formed building material comprising a sequestered-CO₂ component, wherein the sequestered-CO₂ component comprises 25% (w/w) or less gypsum and 75% (w/w) or more calcium carbonate comprising a metastable carbonate selected from the group consisting of amorphous calcium carbonate, vaterite, aragonite, and combinations thereof, wherein the sequestered-CO₂ has a δ¹³C less than −15%, and wherein the formed building material is drywall having a compressive strength ranging from 1 to 20 MPa.

Provided is a method for producing a paver comprising a) producing a metastable sequestered-CO₂ component from a solution of divalent cations and a gaseous waste stream comprising CO₂, wherein the metastable sequestered-CO₂ component, upon contact with freshwater, re-precipitates into a freshwater stable compound; and b) forming the paver from the metastable sequestered-CO₂ component in a process comprising contacting the sequestered-CO₂ component with freshwater. In some embodiments, the paver comprises 5% to 50% (w/w) sequestered-CO₂ component. In some embodiments, the sequestered-CO₂ component comprises carbonates. In some embodiments, the sequestered-CO₂ component further comprises co-products of NOx, SOx, VOCs, particulates, mercury, or a combination thereof resulting from conditions used to convert carbon dioxide to carbonates. In some embodiments, the gaseous waste stream further comprises NOx, SOx, VOCs, particulates, mercury, or a combination thereof. In some embodiments, the paver has a carbon footprint that is neutral or negative. In some embodiments, water for forming the paver is provided by the sequestered-CO₂ component. In some embodiments, the sequestered-CO₂ component provides at least 50% of the water for forming the paver. In some embodiments, the paver continuously reduces carbon emission via reduced lighting demands due to the high albedo of the paver.

Also provided is a paver produced by any of the foregoing methods for producing a paver.

Also provided is a paver comprising a sequestered-CO₂ component, wherein the sequestered-CO₂ component comprises 75% (w/w) or more calcium carbonate comprising a metastable carbonate selected from the group consisting of amorphous calcium carbonate, vaterite, aragonite, and combinations thereof, and wherein the paver has one or more properties selected from the group consisting of one or more paver properties described herein. In some embodiments, the sequestered-CO₂ component further comprises bicarbonates. In some embodiments, the carbonates, the bicarbonates, or the combination thereof has a δ¹³C less than −5%. In some embodiments, the sequestered-CO₂ component further comprises calcite, ikaite, magnesite, barringtonite, nesquehonite, lansfordite, amorphous magnesium carbonate, or a combination thereof. In some embodiments, the sequestered-CO₂ component further comprises calcium, magnesium, or a combination thereof. In some embodiments, the sequestered-CO₂ component further comprises strontium. In some embodiments, the sequestered-CO₂ component further comprises co-products from NOx, SOx, VOCs, particulates, mercury, or a combination thereof. In some embodiments, the sequestered-CO₂ component further comprises sulfates. In some embodiments, the paver, when subjected to a leaching process consisting essentially of preparing 2×1 L of an extraction fluid consisting essentially of an aqueous solution of acetic acid, wherein each 1 L of the extraction fluid consists essentially of 5.7 mL acetic acid in deionized water; grinding the some of the paver such that particles of ground paver are less than 1 cm in the narrowest dimension if the particles are not already less than 1 cm in the narrowest dimension; placing 100 g of the ground paver into an extraction vessel with 2 L of the extraction fluid to produce an extraction composition; rotating the extraction vessel in an end-over-end fashion for 18±2 hours at room temperature; filtering the extraction composition through borosilicate glass fiber with a pore size of 0.6 μm to 0.8 μm to produce a leachate; and adjusting pH of the leachate with IN nitric acid to a pH of pH 2 or less than pH 2, produces a leachate comprising less than 0.2 mg/L of mercury. In some embodiments, the leaching process produces a leachate comprising less than 5.0 mg/L arsenic. In some embodiments, the leaching process produces a leachate comprising less than 100 mg/L barium. In some embodiments, the leaching process produces a leachate comprising less then 1.0 mg/L cadmium. In some embodiments, the leaching process produces a leachate comprising less than 5.0 mg/L chromium. In some embodiments, the leaching process produces a leachate comprising less than 5.0 mg/L lead. In some embodiments, the leaching process produces a leachate comprising less than 1.0 mg/L selenium. In some embodiments, the leaching process produces a leachate comprising less than 5.0 mg/L silver. In some embodiments, the paver, when subjected to a carbon dioxide release protocol consisting essentially of grinding a portion of the paver such that particles of ground paver are less than 1 cm in the narrowest dimension if the particles are not already less than 1 cm in the narrowest dimension and immersing the solid in a solution having a pH between pH 4.8 and pH 5.2 and a temperature between 60 and 80° C. for 48 hours, produces less than 5 grams carbon dioxide per 100 grams solid.

DRAWINGS

A better understanding of different features and advantages will be obtained by reference to the following detailed description that sets forth illustrative embodiments, and the accompanying drawings of which:

FIG. 1 provides a schematic of a production process for a sequestered-CO₂ component.

FIG. 2 provides an X-ray diffraction (“XRD”) diffractogram for precipitation material produced in Example 1.

FIG. 3 provides scanning electron microscope (“SEM”) images of the precipitation material produced in Example 1.

FIG. 4 provides an exemplary method for making pavers.

FIG. 5 provides an assortment of pavers that may be manufactured.

FIG. 6 provides pavers and some properties of the pavers.

FIG. 7 provides SEM images of drywall of different compositions.

FIG. 8 provides properties of drywall of different compositions.

FIG. 9 provides SEM images and XRD diffractograms for cement substitute from 0 to 28 days.

FIG. 10 provides SEM images for cement substitute.

FIG. 11 provides SEM images for cement substitute binding with fine aggregate.

FIG. 12 provides SEM images for cement substitute interacting with conventional cement.

DESCRIPTION

Formed building materials comprising a sequestered-CO₂ component are provided. The building materials described herein include a sequestered-CO₂ component from precipitation material comprising carbonates, bicarbonates, or a combination thereof. Provided are also methods of making and using the formed building materials comprising a sequestered-CO₂ component.

It is to be understood that the particular embodiments described herein may vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and the terminology is not intended to be limiting, since the scope of the invention will be limited only by the appended claims. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the claimed invention belongs.

Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range, is encompassed. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges and are also encompassed, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included.

Certain ranges are presented herein with numerical values being preceded by the term “about.” The term “about” is used herein to provide literal support for the exact number that it precedes, as well as a number that is near to or approximately the number that the term precedes. In determining whether a number is near to or approximately a specifically recited number, the near or approximating unrecited number may be a number, which, in the context in which it is presented, provides the substantial equivalent of the specifically recited number.

All publications, patents, and patent applications cited in this specification are incorporated herein by reference to the same extent as if each individual publication, patent, or patent application were specifically and individually indicated to be incorporated by reference. Furthermore, each cited publication, patent, or patent application is incorporated herein by reference to disclose and describe the subject matter in connection with which the publications are cited. The citation of any publication is for its disclosure prior to the filing date and should not be construed as an admission of prior invention. Further, the dates of publication provided might be different from the actual publication dates, which may need to be independently confirmed.

It is noted that, as used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise. It is further noted that the claims may be drafted to exclude any optional element. As such, this statement is intended to serve as antecedent basis for use of such exclusive terminology as “solely,” “only” and the like in connection with the recitation of claim elements, or use of a “negative” limitation.

As will be apparent to those of skill in the art upon reading this disclosure, each of the individual embodiments described and illustrated herein has discrete components and features that may be readily separated from or combined with the features of any of the other several embodiments. Any recited method can be carried out in the order of events recited or in any other order, which is logically possible. Although any methods and materials similar or equivalent to those described herein may also be used in practice or testing, representative illustrative methods and materials are now described.

Formed Building Materials

In some embodiments, formed building materials comprising a sequestered-CO₂ component are provided, which formed building materials comprise carbon derived from a fuel used by humans, e.g., carbon having a fossil fuel origin. For example, formed building materials comprising a sequestered-CO₂ component contain carbon that was released in the form of CO₂ from the combustion of fuel. In certain embodiments, the carbon sequestered in a composition (e.g., composition comprising sequestered-CO₂) is in the form of carbonates, bicarbonates, or a combination thereof. Therefore, in certain embodiments, formed building materials provided herein may contain, for example, carbonates, wherein at least part of the carbon in the carbonates may be derived from a fuel used by humans (e.g., a fossil fuel). As such, production of formed building materials results in the placement of CO₂ into a storage stable form (e.g., a component of the built environment, such as a man-made structure, such as a building, wall, road, etc.). As such, production of the formed building materials comprising sequestered-CO₂ results in the prevention of CO₂ gas from entering the atmosphere.

Building materials include a sequestered-CO₂ component comprising carbonates, bicarbonates, or a combination thereof. The carbonates, bicarbonates, or the combination thereof are derived from, for example, precipitated from, an aqueous solution as described in greater detail herein, and, as such, may be described herein as precipitation material. Sequestered-CO₂ components store a significant amount of CO₂ in a storage-stable format, such that CO₂ gas is not readily produced from the product and released into the atmosphere. In certain embodiments, the sequestered-CO₂ components may store 50 tons or more of CO₂, such as 100 tons or more of CO₂, including 250 tons or more of CO₂, for instance 500 tons or more of CO₂, such as 750 tons or more of CO₂, including 900 tons or more of CO₂ for every 1000 tons of building material. In certain embodiments, the sequestered-CO₂ component of the building materials comprise about 5% or more of CO₂, such as about 10% or more of CO₂, including about 25% or more of CO₂, for instance about 50% or more of CO₂, such as about 75% or more of CO₂, including about 90% or more of CO₂, e.g., present as one or more carbonate compounds.

The sequestered-CO₂ component (e.g., component comprising carbonates, bicarbonates, or a combination thereof) may include one or more carbonate compounds. The amount of carbonate (or bicarbonate, or combination of carbonate and bicarbonate) in the sequestered-CO₂ component, as determined by, for example, coulometry using the protocol described in coulometric titration, is 40% or higher, such as 70% or higher, including 80% or higher. In some embodiments, where the Mg source is a mafic mineral (described in U.S. patent application Ser. No. 12/501,217, filed 10 Jul. 2009, and U.S. Provisional Patent Application No. 61/079,790, filed 10 Jul. 2008, each of which is incorporated herein by reference) or an ash (described in U.S. application Ser. No. 12/486,692, filed 17 Jun. 2009, and U.S. Provisional Application Ser. No. 61/073,319, filed 17 Jun. 2008, each of which is incorporated herein by reference), the resultant product may be a composition containing silica as well as carbonate. In these embodiments, the carbonate content of the product may be as low as 10%.

The building materials provide for long-term storage of CO₂ in a manner such that CO₂ is sequestered (i.e., fixed) in the building material, where the sequestered CO₂ does not become part of the atmosphere. When the building material is maintained under conditions conventional for its intended use, the building material keeps sequestered CO₂ fixed for extended periods of time (e.g., 1 year or longer, 5 years or longer, 10 years or longer, 25 years or longer, 50 years or longer, 100 years or longer, 250 years or longer, 1000 years or longer, 10,000 years or longer, 1,000,000 years or longer, or even 100,000,000 years or longer) without significant, if any, release of the CO₂ from the building material. With respect to the building materials described herein, when they are employed in their intended use and over their lifetime, the amount of degradation, if any, as measured in terms of CO₂ gas release from the product will not exceed 5% per year, and in certain embodiments will not exceed 1% per year. Indeed, building materials described herein do not release more than 1%, 5%, or 10% of its total CO₂ when exposed to normal conditions of temperature and moisture, including rainfall of normal pH, for its intended use, for at least 1, 2, 5, 10, or 20 years, or for more than 20 years, for example, for more than 100 years. In some embodiments the composition does not release more than 1% of its total CO₂ when exposed to normal conditions of temperature and moisture, including rainfall of normal pH, for its intended use, for at least 1 year. In some embodiments the composition does not release more than 5% of its total CO₂ when exposed to normal conditions of temperature and moisture, including rainfall of normal pH, for its intended use, for at least 1 year. In some embodiments the composition does not release more than 10% of its total CO₂ when exposed to normal conditions of temperature and moisture, including rainfall of normal pH, for its intended use, for at least 1 year. In some embodiments the composition does not release more than 1% of its total CO₂ when exposed to normal conditions of temperature and moisture, including rainfall of normal pH, for its intended use, for at least 10 years. In some embodiments the composition does not release more than 1% of its total CO₂ when exposed to normal conditions of temperature and moisture, including rainfall of normal pH, for its intended use, for at least 100 years. In some embodiments the composition does not release more than 1% of its total CO₂ when exposed to normal conditions of temperature and moisture, including rainfall of normal pH, for its intended use, for at least 1000 years.

Any suitable surrogate marker or test that is reasonably able to predict such stability may be used. For example, an accelerated test comprising conditions of elevated temperature and/or moderate to more extreme pH conditions is reasonably able to indicate stability over extended periods of time. For example, depending on the intended use and environment of the composition, a sample of the composition may be exposed to 50, 75, 90, 100, 120, or 150° C. for 1, 2, 5, 25, 50, 100, 200, or 500 days at between 10% and 50% relative humidity, and a loss less than 1%, 2%, 3%, 4%, 5%, 10%, 20%, 30%, or 50% of its carbon may be considered sufficient evidence of stability of materials for a given period (e.g., 1, 10, 100, 1000, or more than 1000 years).

CO₂ content of the material may be monitored by any suitable method (e.g., coulometry). Other conditions may be adjusted as appropriate, including pH, pressure, UV radiation, and the like, again depending on the intended or likely environment. It will be appreciated that any suitable conditions may be used that one of skill in the art would reasonably conclude indicate the requisite stability over the indicated time period. In addition, if accepted chemical knowledge indicates that the composition would have the requisite stability for the indicated period this may be used as well, in addition to or in place of actual measurements. For example, some carbonate compounds that may be part of a composition (e.g., in a given polymorphic form) may be well-known geologically and known to have withstood normal weather for decades, centuries, or even millennia, without appreciable breakdown, and so have the requisite stability.

Depending upon the particular formed building material the amount of sequestered-CO₂ component (e.g., component comprising carbonates, bicarbonates, or a combination thereof) present in the building material may vary. The sequestered-CO₂ component, which may be unrefined, refined, or otherwise treated precipitation material (e.g., carbonates, bicarbonates, or carbonates and bicarbonates) as described herein, may be used as a partial cement substitute or a complete cement substitute. The sequestered-CO₂ component, though it may or may not be cementitious in and of itself, may react to a some degree, or not, with a cement composition such as ordinary Portland cement (or with concrete-forming materials such as fine aggregate, coarse aggregate, etc.) to ultimately produce a hardened composition. As such, a sequestered-CO₂ component may be combined with a cement composition (e.g., ordinary Portland cement) to produce a hardened cement composition (or concrete if further combined with concrete-forming materials such as fine aggregate, coarse aggregate, etc.) with properties (e.g., compressive strength; porosity; etc) described herein, but without a reaction between the sequestered-CO₂ component and the cement composition (or concrete-forming materials if present). In some embodiments, a sequestered-CO₂ component may be combined with a cement composition (e.g., ordinary Portland cement) to produce a hardened cement composition (or concrete if combined with concrete-forming materials such as fine aggregate, coarse aggregate, etc.) with properties (e.g., compressive strength) described herein, but resulting, at least in part, from reaction between the sequestered-CO₂ component and the cement composition (or concrete-forming materials if present).

A substantial reduction in carbon footprint may result from using formed building materials in which sequestered-CO₂ component is used to the exclusion of any additional cementitious components (e.g., OPC) in the formed building materials. As provided herein, sequestered-CO₂ component (optionally “cement substitute” when used to the exclusion of any other cementitious components) may comprise calcium carbonate polymorphs such as amorphous calcium carbonate, vaterite, aragonite, and/or calcite in the proportions further described herein, and the sequestered-CO₂ component may optionally be used in conjunction with fine and/or coarse aggregate, and further optionally in conjunction with supplementary cementitious materials such fly ash, slag, and/or metakaolin. As such, formed building materials may be reduced-carbon footprint building materials. Reduced-carbon footprint building materials have a reduced carbon footprint compared to conventional formed building materials (e.g., corresponding building materials that lack the sequestered-CO₂ component [e.g., component comprising carbonates, bicarbonates, or a combination thereof]). Using any convenient carbon footprint calculator, the magnitude of carbon footprint reduction of the building materials as compared to corresponding conventional building materials that lack the sequestered-CO₂ component may be 5% or more, such as 10% or more, including 25%, 50%, 75% or even 100% or more. In certain embodiments, the reduced-carbon footprint building materials are carbon neutral, in that they have substantially no, if any, calculated carbon footprint (e.g., as determined using any convenient carbon footprint calculator that is relevant for a particular building material of interest). Carbon neutral building materials include those compositions that exhibit a carbon footprint of 50 lbs CO₂/cu yd material or less, such as 10 lbs CO₂/cu yd material or less, including 5 lbs CO₂/cu yd material or less, where in certain embodiments the carbon neutral materials have 0 or negative lbs CO₂/cu yd material, such as negative 1 or more, e.g., negative 3 or more lbs CO₂/cu yd material. In come instances, the low carbon footprint materials have a significantly negative carbon footprint, e.g., −100 or more lbs CO₂/cu yd or less.

The formed building materials may vary greatly, which formed building materials comprise materials shaped (e.g., molded, cast, cut, or otherwise produced) into man-made structures with defined physical shape, i.e., configuration. Formed building materials are distinct from amorphous building materials (e.g., powder, paste, slurry, etc.) that do not have a defined and stable shape, but instead conform to the container in which they are held, e.g., a bag or other container. Formed building materials are also distinct from irregularly or imprecisely formed materials (e.g., aggregate, bulk forms for disposal, etc.) in that formed building materials are produced according to specifications that allow for use of formed building materials in, for example, buildings. Formed building materials may be prepared in accordance with traditional manufacturing protocols for such structures, with the exception that an amount of sequestered-CO₂ component (e.g., component comprising carbonates, bicarbonates, or a combination thereof) is employed. As described in more detail below, the portion of components replaced with the sequestered-CO₂ component may vary, and in certain instances is 5% by weight or more, including 10% by weight or more, 25% by weight or more, 50% by weight or more, 75% by weight or more, 90% by weight or more, or even 100% by weight. In producing the formed building materials, an amount of the sequestered-CO₂ component may be combined with water and other additional components, which may include, but are not limited to clay, shale, soft slate, calcium silicate, quarried stone, Portland cement, fly ash, slag, metakaolin, cement, aggregate (e.g., blast furnace slag, bottom ash, gravel, limestone, granite, sand, etc.), silica fume and pozzolans.

Illustrative formed building materials according to certain embodiments are reviewed in greater detail below. However, the below review of formed building materials is not limiting, and is provided solely to further describe various exemplary embodiments of formed building materials comprising sequestered-CO₂ components.

Masonry units are formed building materials used in the construction of load-bearing and non-load-bearing structures that are generally assembled using mortar, grout, and the like; however, masonry units need not necessarily be assembled using mortar, grout, and the like. Exemplary masonry units include bricks, blocks, and tiles. Pavers are exemplary masonry units that may or may not use mortar, grout, and the like. Bricks and blocks are polygonal structures possessing linear dimensions. Bricks are masonry units with dimensions (mm) not exceeding 337.5×225×112.5 (length×width×height). Any unit with dimensions (mm) between 337.5×225×112.5 to 2000×1000×500 (length×width×depth) is termed a “block.” Structural units with dimensions (mm) exceeding 2000×1000×500 (length×width×depth) are termed “slabs.” Tiles refer to masonry units that possess the same dimensions as bricks or blocks, but may vary considerably in shape, i.e., may not be polygonal (e.g., hacienda-style roof tiles). Pavers are described in more detail below.

One type of masonry unit provided is a brick, which refers to a structural unit of material used in masonry construction, generally laid using mortar. Bricks are masonry units with dimensions (mm) not exceeding 337.5×225×112.5 (length×width×height). In some embodiments, the bricks may have lengths ranging from 175 to 300 mm, such as 200 to 250 mm, including 200 to 230 mm; widths ranging from 75 to 150 mm, such as 100 to 120 mm, including 100 to 110 mm; and heights ranging from 50 to 90 mm, such as 50 to 80 mm, including 55 to 75 mm Bricks may vary in grade, class, color, texture, size, weight and can be solid, cellular, perforated, frogged, or hollow. Bricks may include but are not limited to building brick, facing brick, load bearing brick, engineering brick, thin veneer brick, paving brick, glazed brick, firebox brick, chemical resistant brick, sewer and manhole brick, industrial floor brick, etc. The bricks may also vary in frost resistance (i.e., frost resistant, moderately frost resistant or non frost resistant), which relates to the durability of bricks in conditions where exposure to water may result in different levels of freezing and thawing. Frost resistant bricks are durable in conditions of constant exposure to water and freezing and thawing. Moderately frost resistant bricks are durable in conditions of sporadic exposure to water and freezing and thawing. Non-frost resistant bricks are not durable in conditions of exposure to water and freezing and thawing. These bricks are suitable only for internal use and are liable to damage by freezing and thawing except when protected by an impermeable cladding during construction. Bricks may also vary in soluble salt content (i.e., low or normal). Percentage by mass of soluble ions in bricks with a low soluble salt content does not exceed 0.03% magnesium, 0.03% potassium, 0.03% sodium, and 0.5% sulfate. Percentage by mass of soluble ions in bricks with a normal salt content does not exceed 0.25% of magnesium, potassium, and sodium in total and sulfate content does not exceed 1.6%. The bricks may vary considerably in physical and mechanical properties. The compressive strength of bricks may range, in certain instances, from 5 to 100 megapascals (MPa), including 20-40 MPa. The flexural strength of bricks may vary, ranging from 0.5 to 10 MPa, including 2 to 7 MPa, such as 2 to 5 MPa. The maximum water absorption of bricks may vary, ranging from 5 to 25%, including 10 to 15%. Bricks may also undergo moisture movement (expansion or contraction) due to the absorption or loss of water to its environment. The dimensional stability (i.e., linear shrinkage or expansion) due to moisture movement may vary, in certain instances ranging from 0.001 to 0.2%, including 0.05 to 0.1%. In some embodiments, the bricks may be used for paving a road. Bricks used to pave areas exposed to heavy traffic (e.g., pedestrian, vehicular, etc.) may have an abrasion resistance index ranging from 0.1 to 0.5, including 0.2 to 0.4, such as 0.3. In addition, bricks may have a volume abrasion loss ranging from 1.0 to 4.0 cm³/cm², including 1.5 to 2.5 cm³/cm², such as 2.0 cm³/cm². The building material composition comprising the sequestered-CO₂ component (e.g., component comprising carbonates, bicarbonates, or a combination thereof) may be molded, extruded, or sculpted into the desired shape and size to form a brick. The shaped composition is then dried and further hardened by hydraulic pressure, autoclave or fired in a kiln at temperatures ranging between 900° to 1200° C., such as 900° to 1100° C. and including 1000° C.

Another type of masonry unit provided is blocks, (e.g., concrete, cement, foundation, etc.). Blocks are distinct from bricks based on their structural dimensions. Specifically, blocks exceed the dimensions (mm) of 337.5×225×112.5 (length×width×height). Blocks may vary in color, texture, size, and weight and can be solid, cellular, and hollow or employ insulation (e.g., expanded polystyrene foam) in the block void volume. Blocks may be load-bearing, non-load-bearing or veneer (i.e., decorative) blocks. In some embodiments, the blocks may have lengths ranging from 300 to 500 mm, such as 350 to 450 mm, widths ranging from 150 to 250 mm, such as 180 to 215 mm and heights ranging from 100 to 250 mm, such as 150 to 200 mm. The blocks may also vary in faceshell thickness. In some instances, the blocks may have faceshell thicknesses ranging from 15 to 40 mm, including 20 to 30 mm, such as 25 mm. The blocks may also vary in web thickness. In some embodiments, the blocks may have web thicknesses ranging from 15 to 30 mm, including 15 to 25 mm, such as 20 mm. The blocks may vary considerably in physical and mechanical properties. The compressive strength of blocks may vary, in certain instances ranging from 5 to 100 MPa, including 15 to 75 MPa, such as 20 to 40 MPa. The flexural strength of blocks may also vary, ranging from 0.5 to 15 MPa, including 2 to 10 MPa, such as 4 to 6 MPa. The maximum water absorption of the blocks may vary, ranging from 7 to 20% by weight including 8 to 15%, such as 9 to 11%. Blocks may also undergo moisture movement (expansion or contraction) due to the absorption or loss of water to its environment. Blocks may be Type I moisture-controlled units or Type II non-moisture-controlled units. The dimensional stability (i.e., linear shrinkage) of the blocks may vary depending on their intended use and/or geographical location of use, in certain instances ranging from 0.02 to 0.15%, such as 0.03 to 0.05%. The building material composition comprising the sequestered-CO₂ component (e.g., component comprising carbonates, bicarbonates, or a combination thereof) may be molded, extruded, or sculpted into the desired shape and size to form a block. Such a building material composition may further comprise fly ash and/or bottom and may be used to produce cinder blocks. The shaped composition may be further compacted by roller compaction, hydraulic pressure, vibrational compaction, or resonant shock compaction. In some instances, the resultant composition may also be foamed using mechanically or chemically introduced gases prior to being shaped or while the composition is setting in order to form a lightweight concrete block. The composition is further cured in an environment with a controlled temperature and humidity.

Another type of building material provided is a tile. Tiles refer to non-load-bearing building materials that are commonly employed on roofs and to pave exterior and interior floors of commercial and residential structures. Some examples where tiles may be employed include, but are not limited to, the roofs of commercial and residential buildings, ceilings (e.g., ceiling tile), decorative patios, bathrooms, saunas, kitchens, building foyer, driveways, pool decks, porches, walkways, sidewalks, and the like. Tiles may take on many forms depending on their intended use and/or intended geographical location of use, varying in shape, size, weight, and may be solid, webbed, cellular or hollow. Tiles may vary in dimension, e.g., lengths ranging from 100 to 1000 mm, including 250 to 500 mm, such as 250 to 300 mm; widths ranging from 50 to 1000 mm, including 100 to 250 mm, such as 125 to 175 mm; and thickness ranging from 10 to 30 mm, including 15 to 25 mm, such as 15 to 20 mm. The compressive strengths of tiles may also vary, in certain instances ranging from 5 to 75 MPa, including 15 to 40 MPa, such as 25 MPa. The flexural strength of tiles may vary, ranging from 0.5 to 7.5 MPa, including 2 to 5 MPa, such as 2.5 MPa. The maximum water absorption of tiles may also vary, in certain instances ranging from 5 to 15%, including 7 to 12%. Tiles may also undergo moisture movement (expansion or contraction) due to the absorption or loss of water to its environment. The dimensional stability (i.e., linear shrinkage or expansion) due to moisture movement may vary, in certain instances ranging from 0.001 to 0.25%, including 0.025 to 0.075%, such as 0.05%. Tiles used to pave areas exposed to heavy traffic (e.g., pedestrian, vehicular, etc.) may have an abrasion resistance index that may vary considerably, ranging from 0.1 to 0.5, including 0.25. In addition, tiles may have a volume abrasion loss ranging from 1.0 to 4.0 cm³/cm², including 1.5 to 3.0 cm³/cm², such as 2.7 cm³/cm². Tiles may be polygonal, circular or take on any other desired shape. As such, the building material composition comprising the sequestered-CO₂ component (e.g., component comprising carbonates, bicarbonates, or a combination thereof), may be molded or cast into the desired tile shape and size. The shaped composition may be further compacted by roller compaction, hydraulic pressure, vibrational compaction, or resonant shock compaction. The resultant composition may also be poured out into sheets or a roller may be used to form sheets of a desired thickness. The sheets are then cut to the desired dimensions of the tiles. In some instances, the resultant composition may also be foamed using mechanically or chemically introduced gases prior to being shaped or while the composition is setting in order to form a lightweight tile. The shaped composition is then allowed to set and further cured in an environment with a controlled temperature and humidity. Tiles may be further polished, colored, textured, shot blasted, inlaid with decorative components and the like.

Another type of formed building material and masonry unit is pavers. Pavers are often used in paving applications such as patios, driveways, sidewalks, walkways, terraces, balconies, courtyards, pools (e.g., surrounding pools, pool coping, etc.), gardens (e.g., pathways, walkways, stepping stones, retaining walls), and edging (e.g., for patios, gardens, driveways, walkways, etc.). Pavers may or may not be used with mortar, grout, and the like. Use of mortar, grout, and the like ultimately depends upon the application of pavers or individual preference. Non-interlocking (e.g., non-dentated pavers, usually basic brick-, block-, or cube-shaped pavers) pavers, for example, may use mortar, grout, and the like; interlocking pavers, for example, are generally used without mortar, grout, and the like. It should be understood that interlocking pavers may be fully interlocking pavers in which pavers may interlock on both axes, or partial interlocking pavers in which pavers may interlock on one axis. Any of the pavers described herein may also be permeable (or non-permeable) as described in more detail below.

Pavers described herein may be manufactured according to standard manufacturing procedures for concrete pavers to have a wide variety of different properties (e.g., compressive strength), colors, shapes, patterns, and sizes. An exemplary method for manufacturing concrete pavers is illustrated in FIG. 4.

Referring to the exemplary paver manufacturing method in FIG. 4, the manufacturing method may begin with weighing raw materials (e.g., ground granulated blast-furnace slag or equivalent, ¼gravel, sand, cement and/or sequestered-CO₂ component in step 410. When all raw materials are weighed and ready, the slag, sand, and gravel may be poured into a mixer, followed by cement, an optional color agent, and water. Any other additives (e.g., admixtures such as water-reducing admixtures, including, but no limited to GLENIUM® 7500; accelerators such as CaCl₂; etc.) may be added at this time, or, alternatively, added at a later time (i.e., “delayed addition”) depending upon the additive and accepted methods of use. The mixing time may vary depending upon the particular materials being mixed. In some embodiments, mixing time may be at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 30, 40, 50, 60, 120, 180, 240, 300 minutes, or possibly more. In some embodiments, mixing time may be less than 300, 240, 180, 120, 60, 50, 40, 30, 20, 15, 10, 9, 8, 7, 6, 5, 4, 3, 2 minutes, or possibly less. Water may be added to attain a desirable mixture consistency. The amount of water used to attain the desirable mixture consistency may depend upon the amount of moisture already in the raw materials, ambient humidity, and other factors during the mixing process. The optional color agent may be added as desired.

In step 430, the mixture (e.g., ground granulated blast-furnace slag or equivalent, ¼ gravel, sand, cement and/or sequestered-CO₂ component) in the mixer may be discharged onto a conveyor to convey the mixture to a block machine hopper. The block machine hopper may subsequently open into a loading filling box. The loading filling box, having been charged with the mixture, may then travel over a paver mold, filling the entire internal chamber of the mold with the mixture (with or without vibration/shaking).

In step 440, a tamper head may come down to apply pressure to the mixture inside the mold using approximately 3 MPa of pressure. In some embodiments, at least 0.3, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, or 30 MPa of pressure may be applied to the mixture inside the mold. In some embodiments, the pressure applied to the mixture inside the mold may be less than 30, 20, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.5, or 0.3 MPa. While pressure is being applied, the mold may be vibrated for approximately 2 seconds. In some embodiments, the mold may vibrated for at least 1, 2, 3, 4, 5, 6, 7, 8 9, 10, 20, 30, 40, 50, or 60 seconds, or possibly more, such as at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 minutes or more. In some embodiments, the mold may be vibrated for less than 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 minute, or possibly less, such as less than 60, 50, 40, 30, 20, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 second.

In step 450, the mold may be raised and the tamper head pushed down to place one or more pavers onto a production board. The production board may then be pushed onto a conveyor and to an inlet elevator. In step 460, the inlet elevator may subsequently fill, and a finger car may pick up a batch of pavers and move them to drying racks. In step 470, the finger car may then transfer the batch of pavers (now cured) to an outlet elevator. In step 480, the production boards may be conveyed to a cuber. Therein, the production boards may pick up a batch of cured pavers and move the pavers onto a pallet for bagging and shipping. In step 490, empty production boards may return to the block machine ending one round of the exemplary paver manufacturing process. Equipment useful for manufacturing pavers of any type described herein is known and existing.

Pavers described herein, through different mixture designs and manufacturing methods, may be designed to have any of a number of different properties. For example, the material and methods described above for manufacturing pavers may be used to prepare a paver having a minimum compressive strength of 8000 psi, which compressive strength is the minimum American Society for Testing and Materials (“ASTM”) requirement for pavers. In some embodiments, pavers described herein may have a compressive strength of at least 250, 500, 750, 1,000, 2,000, 3,000, 4,000, 5,000, 6,000, 7,000, 8,000, 9,000, 10,000, 11,000, 12,000, 13,000, 14,000, 15,000, or 16,000 psi. In some embodiments, pavers described herein may have a compressive strength of less than 16,000, 15,000, 14,000, 13,000, 12,000, 11,000, 10,000, 9,000, 8,000, 7,000, 6,000, 5,000, 4,000, 3,000, 2,000, 1,000, 750, 500, or 250 psi. Other properties that may be varied by mixture designs and/or manufacturing methods includes water absorption, flexural strength, skid resistance, coefficient of friction, freeze-thaw cycle resistance, and the like. With respect to different mixture designs, some exemplary paver mixture designs are included in Tables 1-7 below, wherein, for example, “15% cement” indicates a mixture comprising about 15% of a cement (e.g., ordinary Portland cement (OPC) and the like), sequestered-CO₂ component or precipitation material as described herein, or a combination thereof. Such a cement-sequestered-CO₂ component combination includes, in some embodiments, at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 96, 97, 98, or 99% sequestered-CO₂ component. In some embodiments, less than 99, 98, 97, 96, 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, 9, 8, 7, 6, 5 4, 3, 2, or 1% sequestered-CO₂ component is included in the cement-sequestered-CO₂ component combination. While Tables 1-7 do not include any additional additives, a person having ordinary skill in the art will recognize that any of a number of additives may be added to adjust the properties of the mixture (e.g., flow) and/or the resulting pavers. Coloring agents, for example, may be added to any of the mixture designs below. In addition, or in the alternative, GLENIUM® 7500 may be used as a water-reducing admixture in any of the mixture designs below. In addition, or in the alternative, CaCl₂ may be used as an accelerator in any of the mixture designs below.

TABLE 1 Mix design for pavers comprising about 15% cement. Value in kg Mix Design 20% (¼ 15% Cement Gravel) 25% 30% 35% 40% 45% 50% Slag 600 600 600 600 600 600 600 ¼ Gravel 160 200 240 280 320 360 400 Sand 200 200 200 200 200 200 200 Cement 144 150 156 162 168 174 180

TABLE 2 Mix design for pavers comprising about 16% cement. Value in kg Mix Design 20% (¼ 16% Cement Gravel) 25% 30% 35% 40% 45% 50% Slag 600 600 600 600 600 600 600 ¼ Gravel 160 200 240 280 320 360 400 Sand 200 200 200 200 200 200 200 Cement 153.6 160 166.4 172.8 179.2 185.6 192

TABLE 3 Mix design for pavers comprising about 17% cement. Value in kg Mix Design 20% (¼ 17% Cement Gravel) 25% 30% 35% 40% 45% 50% Slag 600 600 600 600 600 600 600 ¼ Gravel 160 200 240 280 320 360 400 Sand 200 200 200 200 200 200 200 Cement 163.2 170 176.8 183.6 190.4 197.2 204

TABLE 4 Mix design for pavers comprising about 18% cement. Value in kg Mix Design 20% (¼ 18% Cement Gravel) 25% 30% 35% 40% 45% 50% Slag 600 600 600 600 600 600 600 ¼ Gravel 160 200 240 280 320 360 400 Sand 200 200 200 200 200 200 200 Cement 172.8 180 187.7 194.4 201.6 208.8 216

TABLE 5 Mix design for pavers comprising about 19% cement. Value in kg Mix Design 20% (¼ 19% Cement Gravel) 25% 30% 35% 40% 45% 50% Slag 600 600 600 600 600 600 600 ¼ Gravel 160 200 240 280 320 360 400 Sand 200 200 200 200 200 200 200 Cement 182.4 190 197.6 205.2 212.8 220.4 228

TABLE 6 Mix design for pavers comprising about 20% cement. Value in kg Mix Design 20% (¼ 20% Cement Gravel) 25% 30% 35% 40% 45% 50% Slag 600 600 600 600 600 600 600 ¼ Gravel 160 200 240 280 320 360 400 Sand 200 200 200 200 200 200 200 Cement 192 200 208 216 224 323 240

TABLE 7 Mix design for pavers comprising about 21% cement. Value in kg Mix Design 20% (¼ 21% Cement Gravel) 25% 30% 35% 40% 45% 50% Slag 600 600 600 600 600 600 600 ¼ Gravel 160 200 240 280 320 360 400 Sand 200 200 200 200 200 200 200 Cement 201.6 210 218.4 226.8 235.2 243.65 252 As described above, Table 1-7 are exemplary mixture designs. As such, the 15-21% cement designs may be modified to include more or less of the cement component, and, optionally, less or more of the slag component, respectively. In such mixture designs, the cement component may be at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 96, 97, 98, or 99% by weight. In some embodiments, the cement component may be less than 99, 98, 97, 96, 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 20, 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1% by weight.

Pavers may be of any desirable color, whether monotone or multicolor, and methods for introducing color into concrete pavers during their manufacture is well known. Pavers may be a natural light grey to white, which color may be possible without the addition of any additional color additives. For example, the larger the proportion of sequestered-CO₂ component in a concrete paver, the whiter the paver will be (absent other color additives [except whitening agents such as TiO₂ {e.g., titanium white, Pigment White 6, CI 77891, etc.}]). Such a paver may have a high albedo, which, in turn, may continually reduce carbon emissions via reduced lighting demands (e.g., due to consuming less electricity from CO₂-producing power plants). Because pavers described herein may be manufactured in many different colors, they too may be manufactured to register a particular reflectance. In some embodiments, for example, a paver may be prepared having a reflectance of at least 0.3 (e.g., as measured by a albedometer). In other embodiments, pavers may be prepared having a reflectance of greater than or less than 0.3 as the application or personal preference demands. Pavers having different reflectance values (e.g., some less than 0.3, some more than 0.3) may be combined to effect a paver surface having a combined reflectance, which, as above, may continually reduce carbon emissions via reduced lighting demands.

A paver, when viewed from above (despite the presence of beveled edges over square edges, each of which is possible for a paver described herein) may have a two-dimensional shape selected from the group consisting of a triangle, an octagon, a hexagon, a pentagon, a circle, a half circle, an oval, a zigzag, a keyhole, a diamond, a fan, a parallelogram, a rectangle, a square, an X-shape, and a W-shape. Other shapes, too, are possible, including combinations of the foregoing. It should be understood that pavers are three-dimensional objects and that the foregoing description applies when viewing a paver from directly above (or directly below). For example, a paver might appear as a rectangle when viewed from directly above, but such a paver will appear to be in the shape of a brick when viewed from an angle other than from directly above. Likewise, a paver might appear as a square when viewed from directly above, but such a paver will appear to be in the shape of a brick or block or cube when viewed from an angle other than from directly above. FIG. 5 provides an illustration of some of the foregoing pavers, and includes some additional pavers that may be manufactured as described herein. The thickness of the foregoing pavers may vary. Concrete pavers may range in thickness depending upon the desired application. Commonly, pavers range from about 1 cm thick to about 12 cm thick. As such, a paver may be at least 1 cm, 2 cm, 3 cm, 4 cm, 5 cm, 6 cm, 7 cm, 8 cm, 9 cm, 10 cm, 11 cm, 12 cm thick. A paver may also be less than 1 cm, 2 cm, 3 cm, 4 cm, 5 cm, 6 cm, 7 cm, 8 cm, 9 cm, 10 cm, 11 cm, 12 cm thick. It should be noted that pavers described herein are not limited to the foregoing thicknesses as a paver, depending upon the application may exceed 12 cm thick. Commonly, pavers have a thickness between 6 cm to 8 cm, wherein 6 cm-thick pavers are generally accepted for pedestrian use (and light vehicle applications), and wherein 8 cm-pavers are generally accepted for heavy vehicular and industrial applications.

Pavers, such as those described herein, may have shapes that are further defined by one or more aspect ratios, including the length-to-width ratio and the length-to-thickness ratio. Aspect ratios are generally used to evaluate the paving units flexural capacity to sustain load without cracking. Regarding the length-to-width ratio, it is generally between 2:1 and 3:1, and it can be determined by dividing the longer surface dimension of a paver by the shorter surface dimension. Regarding the length-to-thickness ratio of a paver, it can be determined by dividing the longest surface dimension of a paver by the thickness. Pavers having length-to-thickness ratios between 3:1 and 4:1 are acceptable for light to medium vehicular applications. Pavers having a length-to-thickness ratio that exceeds 4:1 should not be used in vehicular applications, and optionally, might be used for any other application (e.g., walkways) described herein requiring less robust pavers. For example, a paver measuring 4″×8″×2⅜″ yields an aspect ratio of 3.4:1, which is suitable light to medium vehicular traffic. A paver measuring 12″×12″×2⅜″ yields an aspect ratio of 5:1, which is not suitable for vehicular applications. Given the description of paver aspect ratios for certain applications and the above range of paver thicknesses, a person having ordinary skill in the art will recognize preferred paver dimensions for certain applications. For example, a paver prepared in accordance with the methods described herein for light to medium vehicular applications (e.g., length-to-thickness aspect ratio of 3:1 to 4:1) may have a length-to-thickness ratio of 3.4:1 and a thickness of 2⅜″. Such a paver would, in one embodiment, have a surface length and width of 12″.

As described in U.S. patent application Ser. No. 12/716,236, filed 2 Mar. 2010, titled “Gas Stream Multipollutants Control Systems and Methods,” compositions manufactured using sequestered-CO₂ component described herein, including pavers, might contain, in one form or another, metals such as As, Ag, Ba, Be, Cd, Co, Cr, Cu, Hg, Mo, Ni, Pb, Se, Sb, Tl, V, or Zn, or combinations thereof, as well as other chemical species that might be considered contaminants if released into the environment. Such metals and contaminants may directly result from use of CO₂-containing flue gas (e.g., from a coal-fired power plant), which flue gas may contain said metals as well as SOx, NOx, acid gases, etc. Potential for release of contaminants into the environment may be tested by mixing the composition (e.g., a paver) with an extraction solution, agitating the resultant mixture, and filtering the agitated mixture to produce a testable leachate. Compositions (e.g., pavers) may be tested using any of a variety of tests as different tests have been developed to simulate different environmental conditions. Such tests include, but are not limited to, Toxicity Characteristic Leaching Procedure (TCLP; US EPA Method 1311), Extraction Procedure Toxicity Test (EP-Tox; US EPA Method 1310), Synthetic Precipitation Leaching Procedure (SPLP; US EPA Method 1312), California Waste Extraction Test (WET; California Code of Regulations), Soluble Threshold Limit Concentration (STLC; California Code of Regulations), American Society for Testing and Materials Extraction Test (ASTM D 3987-85), and Multiple Extraction Procedure (MEP; US EPA Method 1320), as such tests and limits defined is such tests exist on the filing date of this patent application. Regulatory water extraction test conditions as defined by waste control regulations in, for example, the United Kingdom, Thailand, Japan, Switzerland, Germany, Sweden, the Netherlands may also be used. Such tests may differ in, for example, extraction solutions, liquid to solid (L/S) ratios, and/or number and duration of extractions. Regarding extract solutions, such tests commonly use aqueous acetic acid, aqueous citric acid, distilled water, synthetic rainwater, or carbonated water.

Pavers may also be engraved (e.g., for a commemorative occasion) such that each has a unique pattern, or such that when used to pave a surface, the surface comprises a unique pattern. In some embodiments, the foregoing pavers may comprise lights (e.g., pavers having lights built in) for decorative or safety purposes.

Construction panels are formed building materials employed in a broad sense to refer to any non-load-bearing structural element that are characterized such that their length and width are substantially greater than their thickness. Exemplary construction panels include cement boards, fiber-cement sidings, and drywall. Construction panels are polygonal structures with dimensions that vary greatly depending on their intended use. The dimensions of construction panels may range from 50 to 500 cm in length, including 100 to 300 cm, such as 250 cm; width ranging from 25 to 200 cm, including 75 to 150 cm, such as 100 cm; thickness ranging from 5 to 25 mm, including 7 to 20 mm, including 10 to 15 mm Cement boards comprise construction panels conventionally prepared as a combination of cement and fiberglass and possess additional fiberglass reinforcement at both faces of the board. Fiber-cement sidings comprise construction panels conventionally prepared as a combination of cement, aggregate, interwoven cellulose, and/or polymeric fibers and possess a texture and flexibility that resembles wood. Drywall comprises construction panels conventionally prepared from gypsum plaster (i.e., semi-hydrous form of calcium sulfate), fibers (glass or paper) and is sandwiched between two sheets of outer material, e.g., paper or fiberglass mats.

One type of construction panel provided is cement board. They are formed building materials where in some embodiments, are used as backer boards for ceramics that may be employed behind bathroom tiles, kitchen counters, backsplashes, etc. and may have lengths ranging from 100 to 200 cm, such as 125 to 175 cm, e.g., 150 to 160 cm; a breadth ranging from 75 to 100 cm, such as 80 to 100 cm, e.g., 90 to 95 cm, and a thickness ranging from 5 to 25 mm, e.g., 5 to 15 mm, including 5 to 10 mm Cement boards may vary in physical and mechanical properties. In some embodiments, the flexural strength may vary, ranging between 1 to 7.5 MPa, including 2 to 6 MPa, such as 5 MPa. The compressive strengths may also vary, ranging from 5 to 50 MPa, including 10 to 30 MPa, such as 15 to 20 MPa. In some embodiments, cement boards may be employed in environments having extensive exposure to moisture (e.g., commercial saunas). The maximum water absorption of the cement boards may vary, ranging from 5 to 15% by weight, including 8 to 10%, such as 9%. Cement boards may also undergo moisture movement (expansion or contraction) due to the absorption or loss of water to its environment. The dimensional stability (i.e., linear shrinkage or expansion) due to moisture movement may vary, in certain instances ranging from 0.035 to 0.1%, including 0.04 to 0.08%, such as 0.05 to 0.06%. The building composition comprising the sequestered-CO₂ component (e.g., component comprising carbonates, bicarbonates, or a combination thereof) may be used to produce the desired shape and size to form a cement board. In addition, a variety of further components may be added to the cement boards which include but are not limited to: plasticizers, foaming agents, accelerators, retarders and air entrainment additives. The building material composition comprising the sequestered-CO₂ component may then be poured out into sheet molds or a roller may be used to form sheets of a desired thickness. The shaped composition may be further compacted by roller compaction, hydraulic pressure, vibrational compaction, or resonant shock compaction. The sheets are then cut to the desired dimensions of the cement boards. In some instances, the resultant composition may also be foamed using mechanically or chemically introduced gases prior to being shaped or while the composition is setting in order to form a lightweight cement board. The shaped composition is then allowed to set and further cured in an environment with a controlled temperature and humidity. The cement boards then may be covered in a fiberglass mat on both faces of the board. Where desired, the cement boards may also be prepared using chemical admixtures such that they possess increased fire, water, and frost resistance as well as resistance to damage by bio-degradation and corrosion. The cement board may also be combined with components such as dispersed glass fibers, which may impart improved durability, increased flexural strength, and a smoother surface.

Another type of construction panel provided is fiber-cement siding. Fiber-cement sidings are formed building materials used to cover the exterior or roofs of buildings and include, but are not limited to building sheets, roof panels, ceiling panels, eternits, and the like. They may also find use as a substitute for timber fascias and barge boards in high fire areas. Fiber-cement sidings may have dimensions that vary, ranging from 200 to 400 cm in length, e.g., 250 cm and 50 to 150 cm in width, e.g., 100 cm and a thickness ranging from 4 to 20 mm, e.g., 5 to 15 mm, including 10 mm Fiber-cement sidings may possess physical and mechanical properties that vary. In some embodiments, the flexural strength may range between 0.5 to 5 MPa, including 1 to 3 MPa, such as 2 MPa. The compressive strengths may also vary, in some instances ranging from 2 to 25 MPa, including 10 to 15 MPa, such as 10 to 12 MPa. In some embodiments, fiber-cement sidings may be employed on buildings that are subject to varying weather conditions, in some embodiments ranging from extremely arid to wet (i.e., low to high levels of humidity). Accordingly, the maximum water absorption of the fiber-cement sidings may vary, ranging from 10 to 25% by mass, including 10 to 20%, such as 12 to 15%. The dimensional stability (i.e., linear shrinkage or expansion) due to moisture movement may vary, in certain instances ranging from 0.05 to 0.1%, including 0.07 to 0.09%. The building composition comprising the sequestered-CO₂ component (e.g., component comprising carbonates, bicarbonates, or a combination thereof) may be used to produce the desired shape and size to form a fiber-cement siding. In addition, a variety of further components may be added to the fiber-cement sidings which include but are not limited to: cellulose fibers, plasticizers, foaming agents, accelerators, retarders and air entrainment additives. The building material composition comprising the sequestered-CO₂ component may then be poured into sheet molds or a roller is used to form sheets of a desired thickness. The shaped composition may be further compacted by roller compaction, hydraulic pressure, vibrational compaction, or resonant shock compaction. The sheets are then cut to the desired dimensions of the fiber-cement sidings. In some instances, the resultant composition may also be foamed using mechanically or chemically introduced gases prior to being shaped or while the composition is setting in order to form a lightweight fiber-cement siding. The shaped composition is then allowed to set and further cured in an environment with a controlled temperature and humidity. The fiber-cement sidings may then be covered with a polymeric film, enamel or paint. Where desired, the fiber-cement sidings may also be prepared using chemical admixtures such that they possess increased fire, water, and frost resistance as well as resistance to damage by bio-degradation and corrosion.

Another type of construction panel provided herein is drywall, which, conventionally, refers to a manufactured building material comprising gypsum used to finish construction of interior walls and ceilings. Such drywall comprises an inner core of gypsum, which inner core is sandwiched between a lining material (e.g., paper or fiberglass). Drywall provided herein comprises an inner core comprising at least some amount of a sequestered-CO₂ component (e.g., component comprising carbonates, bicarbonates, or a combination thereof), if the inner core is not entirely sequestered-CO₂ component, as it is in some embodiments. Utilizing an amount of sequestered-CO₂ component helps reduce the carbon footprint of otherwise conventional drywall by substituting CaSO₄.0.5H₂O used in the preparation of drywall with a component (e.g., sequestered-CO₂ component) derived from CO₂ emissions. The carbon footprint of otherwise conventional drywall is thus lowered due to the replacement of CaSO₄.2H₂O (“gypsum”) in drywall, which gypsum is rehydrated and recrystallized from a CaSO₄.0.5H₂O feedstock, and which feedstock is commonly known as “calcined gypsum” due to the energy-intensive calcination (e.g., 150-160° C. until ˜75% of the water in gypsum is evaporated) used in its production. As such, a drywall slurry used in production of the inner core of drywall may comprise at least 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 99%, 99.9%, or 100% (w/w) sequestered-CO₂ component (e.g. carbonates, bicarbonates, or a combination of carbonates and bicarbonates), the remainder of the drywall slurry being conventional material such as CaSO₄.0.5H₂O. Drywall slurry used in production of the inner core of drywall may comprise less than 100%, 99.9%, 99%, 95%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, 5%, or 1% (w/w) sequestered-CO₂ component (e.g. carbonates, bicarbonates, or a combination of carbonates and bicarbonates), the remainder of the drywall slurry being conventional material such as CaSO₄.0.5H₂O. Combinations of the foregoing are also possible. For example, in some embodiments, a drywall slurry used in production of the inner core of drywall may comprise at least 1% and less than 100% (w/w) sequestered-CO₂ component, at least 50% and less than 100% sequestered-CO₂ component, at least 75% and less than 100% sequestered-CO₂ component, and the like, the remainder of the drywall slurry being conventional material such as CaSO₄.0.5H₂O. The sequestered-CO₂ component in such drywall slurries may be, as indicated, carbonates, bicarbonates, or a combination of carbonates and bicarbonates. In some embodiments, the sequestered-CO₂ component comprises metastable carbonates such as amorphous calcium carbonate, vaterite, and aragonite. As described herein, metastable carbonates, upon addition of fresh water or washing with fresh water (e.g., to remove stabilizing components) facilitates the thermodynamic transformation of metastable carbonate compounds to more stable carbonate compounds (e.g., calcite). Using this thermodynamic driving force, drywall slurry comprising metastable carbonates such as amorphous calcium carbonate, vaterite, and aragonite, optionally with an amount of CaSO₄.0.5H₂O, may form stable carbonates (or more stable [e.g., less metastable] carbonates), optionally with an amount of gypsum, in the final drywall product. As such, the inner core of drywall product may comprise at least 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 99%, 99.9%, or 100% (w/w) sequestered-CO₂ component (e.g. carbonates, bicarbonates, or a combination of carbonates and bicarbonates) such as calcite, the remainder of the inner core being conventional material such as gypsum. The inner core of drywall product may comprise less than 100%, 99.9%, 99%, 95%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, 5%, or 1% (w/w) sequestered-CO₂ component (e.g. carbonates, bicarbonates, or a combination of carbonates and bicarbonates) such as calcite, the remainder of the inner core being conventional material such as gypsum. Combinations of the foregoing are also possible. For example, in some embodiments, the inner core of drywall product may comprise at least 1% and less than 100% (w/w) sequestered-CO₂ component (e.g., calcite), at least 50% and less than 100% sequestered-CO₂ component (e.g., calcite), at least 75% and less than 100% sequestered-CO₂ component (e.g., calcite), and the like, the remainder of the inner core being conventional material such as gypsum. Material prepared from CaSO₄ and Na₂CO₃ as described in U.S. Provisional Patent Application 61/514,879, filed 3 Aug. 2011, which application is incorporated herein by reference, may also be used as sequestered-CO₂ component in place of conventional drywall material. FIG. 7 provides SEM images of different drywall products described herein, one of which comprises 10% sequestered-CO₂ component, specifically, 10% NaHCO₃ in combination with gypsum. Vaterite may also be used at the sequestered-CO₂ component, and depending upon whether transformation to less stable polymorphs has occurred or not, may be present in the drywall product. FIG. 7 also provides an SEM image a drywall product comprising 10% sequestered-CO₂ component, specifically, 10% vaterite in combination with gypsum. Drywall comprising sequestered-CO₂ component meets or exceeds ASTM drywall specifications (e.g., flexural strength, hardness, nail pull resistance), while adding value, including higher strength, lower density, improved thermal properties (e.g., decomposition of sequestered-CO₂ component [e.g., bicarbonate] in fire, which CO₂ has fire extinguishing capabilities), foam textures, decreased solubility (especially with carbonate substitution), sound proofing, odor removal, increased fire protection, and antimicrobial properties (e.g., owing to higher alkalinity of drywall comprising sequestered-CO₂ component). FIG. 8 provides a plot of compressive strength (MPa or psi) versus drywall (“board”) density for an industrial reference and drywall product described herein. As shown, the drywall products (e.g., 10% vaterite/90% gypsum; 20% vaterite/80% gypsum) closely conform to the industrial reference.

In producing drywall comprising a sequestered-CO₂ component, an amount of CaSO₄.0.5H₂O (if gypsum is to be present in the drywall product) and sequestered-CO₂ component (e.g., dried sequestered-CO₂ component), each of which may be pre-ground to a particular fineness, may be mixed with water, optionally comprising additives, and optionally comprising paper pulp, to produce a drywall slurry. If the CO₂-sequestration process is integrated with the manufacturing of drywall product, it may not be necessary to dewater the slurry comprising the precipitation material in process water; instead, the slurry comprising the precipitation material in process water may be used as the drywall slurry, optionally, with an amount of process water removed to provide the appropriate slurry concentration. Additives to the drywall slurry may include, but are not limited to, anti-desiccants (e.g. starch, either acid-modified starch or natural starch made from corn, potato, and/or wheat stock), plasticizers, fibrous materials (e.g. wood fibers, dry paper fibers, cellulose fibers, perlite, fiberglass and/or glass fibers) to lower drywall product density and to increase physical properties, accelerators (e.g., fine gypsum powder; ground land plaster; potassium sulfate; potash; etc.), set retarders (e.g. diethylene triamine pentaacetic acid [“DTPA”]; EDTA; etc), foaming agents (e.g., alkyl ether sulfate or ammonium alkyl ethoxy sulfate) to decrease density in the drywall product, and agents for mildew resistance and fire resistance (e.g., fiberglass; vermiculite; boric acid; etc.). Additional additives (e.g., polyvinyl alcohol) may be used for reinforcing drywall (or any formed building materials described herein), some of which may be found in U.S. Provisional Patent Application No. 61/541,735, filed 30 Sep. 2011, titled “Cement and Concrete with Reinforced Material,” which application is incorporated herein by reference in its entirety. It should be noted here that bicarbonate, if present in the sequestered-CO₂ component, may be decomposed (e.g., with acid such as HCl or H₂SO₄, optionally electrochemically produced as described herein) under controlled conditions to generate carbon dioxide, avoiding the use of additional chemical foaming agents. In addition, recycled materials may be added to the drywall slurry mixture, the recycled materials selected from the group consisting of fly ash, slag, cement kiln dust, and combinations thereof. The drywall slurry, obtained after blending an amount of CaSO₄.0.5H₂O (if gypsum to be present in drywall product) and sequestered-CO₂ component with water, may be deposited between two sheets of backing material (e.g., paper; fiberglass, etc.) and cured to evaporate any residual water. Surprisingly, due to the unique properties of sequestered-CO₂ component, especially when the sequestered-CO₂ component comprise metastable carbonates (e.g., vaterite), it has been found that drywall slurry comprising sequestered-CO₂ component may be molded to produce a drywall product without a backing material. For example, a drywall slurry mixture comprising vaterite, optionally with added CaSO₄.0.5H₂O, may be molded to ultimately form a drywall product without a backing material. Any CaSO₄.0.5H₂O present in the foregoing drywall slurry mixtures may be rehydrated and converted to CaSO₄.2H₂O (“gypsum”). And, as above, any metastable carbonates (e.g., vaterite) present in the sequestered-CO₂ component may re-precipitate to more stable carbonates (e.g., calcite). After removal of residual water, drywall may then be cut for commercial use as a building material.

The dimensions of the drywall building materials may vary, in certain instances ranging from 100 to 200 cm, such as 125 to 175 cm, e.g., 150 to 160 cm in length; ranging from 75 to 100 cm, such as 80 to 100 cm, e.g., 90 to 95 cm in breadth, and ranging from 5 to 50 mm, e.g., 5 to 30 mm, including 10 to 25 mm in thickness. Drywall provided may possess physical and mechanical properties that vary considerably, and may depend upon the amount of the conventional constituents of drywall preparation that are replaced with the composition comprising the sequestered-CO₂ component (e.g., component comprising carbonates, bicarbonates, or a combination thereof). The flexural and compressive strengths of drywall comprising sequestered-CO₂ component are generally larger than conventional drywall, which is known to be a soft construction material. In some embodiments, the flexural strength may range between 0.1 to 3 MPa, including 0.5 to 2 MPa, such as 1.5 MPa. The compressive strengths may also vary, as described herein for formed building materials comprising sequesterd-CO₂. In some instances, the compressive strength of drywall comprising sequesterd-CO₂ component may range from 1 to 40 MPa, 1 to 30 MPa, 1 to 20 MPa, 5 to 15 MPa, or 8 to 10 MPa. The maximum water absorption of drywall may vary, ranging from 2 to 10% by mass, including 4 to 8%, such as 5%. It has also been found that drywall described herein that comprises sequesterd-CO₂ component has better insulation properties than conventional drywall, better acoustic properties than conventional drywall, and better fire resistance properties than conventional drywall. In addition, with respect to strength and porosity, drywall described herein that comprises sequesterd-CO₂ component has been found to have a higher strength than conventional drywall at a given porosity. As such, the drywall provided herein can be more porous (e.g., have a porosity given herein) than conventional drywall, yet be as strong or stronger (e.g., compressive strength; flexural strength; etc., as provided herein) than conventional drywall. Decomposition or combustion of conventional drywall releases sulfuric dioxide (SO₂) and hydrogen sulfide (H₂S), two toxic gases and notable precursors of acid deposition associated with soils and water acidification. Sulfate leaching of conventional drywall may also contaminate groundwater. Replacement of some or all of the CaSO₄ in conventional drywall with sequestered-CO2 component lessens the amount of sulfuric dioxide (SO₂) and hydrogen sulfide (H₂S) that can be released up decomposition of combustion of the drywall provided herein. An additional advantage of using less CaSO4 in drywall is that less sulfate may contaminate groundwater.

Another building material provided is a conduit. Conduits are tubes or analogous structures configured to convey a gas or liquid, from one location to another. Conduits may include any of a number of different structures used in the conveyance of a liquid or gas that include, but are not limited to pipes, culverts, box culverts, drainage channels and portals, inlet structures, intake towers, gate wells, outlet structures, and the like. Conduits may vary considerably in shape, which is generally determined by hydraulic design and installation conditions. Shapes of conduits may include, but are not limited to circular, rectangular, oblong, horseshoe, square, etc. Multiple cell configurations of conduits are also possible. Conduit design may vary depending on its intended use. As such, conduits may have dimensions that vary considerably. Conduits may have outer diameters which range in length from 5 to 500 cm or longer, such as 10 to 300 cm, e.g., 25 to 250 cm. The wall thicknesses may vary considerably, ranging in certain instances from 0.5 to 25 cm or thicker, such as 1 to 15 cm, e.g., 1 to 10 cm. In certain embodiments, conduits may be designed in order to support high internal pressure from water flow within the conduit. In yet other embodiments, conduits may be designed to support high external loadings (e.g., earth loads, surface surcharge loads, vehicle loads, external hydrostatic pressures, etc.). Accordingly, the compressive strength of the walls of conduits may also vary, depending on the size and intended use of the conduit, in some instances ranging, from 5 to 75 MPa, such as 10 to 50 MPa, e.g., 15 to 40 MPa. Where desired, the conduits may be employed with various coatings or liners (e.g., polymeric), and may be configured for easy joining with each other to produce long conveyance structures made up of multiple conduits. In producing conduits, the building material composition comprising the sequestered-CO₂ component (e.g., component comprising carbonates, bicarbonates, or a combination thereof) may be poured into a mold in order to form the desired conduit shape and size. The shaped composition may be further compacted by roller compaction, hydraulic pressure, vibrational compaction, or resonant shock compaction. In some instances, the resultant composition may also be foamed using mechanically or chemically introduced gases prior to being shaped or while the composition is setting in order to form a lightweight conduit structure. The shaped composition is further allowed to set and is cured in an environment with a controlled temperature and humidity. In addition, the conduits may include a variety of further components, such as but not limited to: plasticizers, foaming agents, accelerators, retarders and air entrainment additives. Where desired, the further components may include chemical admixtures such that the conduits possess increased resistance to damage by bio-degradation, frost, water, fire and corrosion. In some embodiments, the conduits may employ structural support components such as, but not limited to, cables, wires and mesh composed of steel, polymeric materials, ductile iron, aluminum or plastic.

Another building material provided is basins. The term basin may include any configured container used to hold a liquid, such as water. As such, a basin may include, but is not limited to structures such as wells, collection boxes, sanitary manholes, septic tanks, catch basins, grease traps/separators, storm drain collection reservoirs, etc. Basins may vary in shape, size, and volume capacity. Basins may be rectangular, circular, spherical, or any other shape depending on its intended use. In some embodiments, basins may possess a greater width than depth, becoming smaller toward the bottom. The dimensions of the basin may vary depending on the intended use of the structure (e.g., from holding a few gallons of liquid to several hundred or several thousand or more gallons of liquid). The wall thicknesses may vary considerably, ranging in certain instances from 0.5 to 25 cm or thicker, such as 1 to 15 cm, e.g., 1 to 10 cm. Accordingly, the compressive strength may also vary considerably, depending on the size and intended use of the basin, in some instances ranging, from 5 to 60 MPa, such as 10 to 50 MPa, e.g., 15 to 40 MPa. In some embodiments, the basin may be designed to support high external loadings (e.g., earth loads, surface surcharge loads, vehicle loads, etc.). In certain other embodiments, the basins may be employed with various coatings or liners (e.g., polymeric), and may be configured so that they may be combined with conveyance elements (e.g., drainage pipe). In other embodiments, basins may be configured so that they may be connected to other basins so that they may form a connected series of basins. In producing basins, the building material composition comprising the sequestered-CO₂ component (e.g., component comprising carbonates, bicarbonates, or a combination thereof) may be poured into a mold to form the desired basin shape and size. The shaped composition may be further compacted by roller compaction, hydraulic pressure, vibrational compaction, or resonant shock compaction. The basins may also be prepared by pouring the composition into sheet molds and the basins further assembled by combining the sheets together to form basins with varying dimensions (e.g., polygonal basins, rhomboidal basins, etc.). In some instances, the resultant composition may also be foamed using mechanically or chemically introduced gases prior to being shaped or while the composition is setting in order to form a lightweight basin structure. The shaped composition is further allowed to set and is cured in an environment with a controlled temperature and humidity. In addition, the basins may include a variety of further components, such as but not limited to: plasticizers, foaming agents, accelerators, retarders and air entrainment additives. Where desired, the further components may include chemical admixtures such that the basins possess increased resistance to damage by bio-degradation, frost, water, fire and corrosion. In some embodiments, the basins may employ structural support components such as, but not limited to cables, wires and mesh composed of steel, polymeric materials, ductile iron, aluminum or plastic.

Another building material provided by is a beam, which, in a broad sense, refers to a horizontal load-bearing structure possessing large flexural and compressive strengths. Beams may be rectangular cross-shaped, C-channel, L-section edge beams, I-beams, spandrel beams, H-beams, possess an inverted T-design, etc. Beams may also be horizontal load-bearing units, which include, but are not limited to joists, lintels, archways and cantilevers. Beams generally have a much longer length than their longest cross-sectional dimension, where the length of the beam may be 5-fold or more, 10-fold or more, 25-fold or more, longer than the longest cross-sectional dimension. Beams may vary in their mechanical and physical properties. For example, unreinforced concrete beams may possess flexural capacities that vary, ranging from 2 to 25 MPa, including 5 to 15 MPa, such as 7 to 12 MPa and compressive strengths that range from 10 to 75 MPa, including 20 to 60 MPa, such as 40 MPa. Structurally reinforced concrete beams may possess considerably larger flexural capacities, ranging from 15 to 75 MPa, including as 25 to 50 MPa, such as 30 to 40 MPa and compressive strengths that range from 35 to 150 MPa, including 50 to 125 MPa, such as 75 to 100 MPa. The beams may be internal or external, and may be symmetrically loaded or asymmetrically loaded. In some embodiments, beams may be composite, wherein it acts compositely with other structural units by the introduction of appropriate interface shear mechanisms. In other embodiments, beams may be non-composite, wherein it utilizes the properties of the basic beam alone. In producing beams, the building material composition comprising sequestered-CO₂ component (e.g., component comprising carbonates, bicarbonates, or a combination thereof) may be poured into a beam mold or cast around a correlated steel reinforcing beam structure (e.g., steel rebar). In some embodiments, the steel reinforcement is pretensioned prior to casting the composition around the steel framework. In other embodiments, beams may be cast with a steel reinforcing cage that is mechanically anchored to the concrete beam. The beams may also employ additional structural support components such as, but not limited to cables, wires and mesh composed of steel, ductile iron, polymeric fibers, aluminum or plastic. The structural support components may be employed parallel, perpendicular, or at some other angle to the carried load. The molded or casted composition may be further compacted by roller compaction, hydraulic pressure, vibrational compaction, or resonant shock compaction. The composition is further allowed to set and is cured in an environment with a controlled temperature and humidity. In addition, the beams may include a variety of further components, such as but not limited to: plasticizers, foaming agents, accelerators, retarders and air entrainment additives. Where desired, the further components may include chemical admixtures such that the beams possess increased resistance to damage by bio-degradation, frost, water, fire and corrosion.

Another building material is a column, which, in a broad sense, refers to a vertical load-bearing structure that carries loads chiefly through axial compression and includes structural elements such as compression members. Other vertical compression members may include, but are not limited to pillars, piers, pedestals, or posts. Columns may be rigid, upright supports, composed of relatively few pieces. Columns may also be decorative pillars having a cylindrical or polygonal, smooth or fluted, tapered or straight shaft with a capital and usually a base, among other configurations. The capital and base of the column may have a similar shape as the column or may be different. Any combination of shapes for the capital and base on a column are possible. Polygonal columns possess a width that is not more than four times its thickness. Columns may be constructed such that they are solid, hollow (e.g., decorative columns), reinforcement filled, or any combination thereof. Columns may be short columns (i.e., columns where strength is governed by construction components and the geometry of its cross section) or slender columns (i.e., cross-sectional dimensions that are less than 5 times its length). The dimensions of the column may vary greatly depending on the intended use of the structure, e.g., from being less than a single story high, to several stories high or more, and having a corresponding width. Columns may vary in their mechanical and physical properties. Properties such as compressive and flexural strengths may vary depending on the design and intended use of the column. For example, unreinforced concrete columns may possess flexural strengths that range from 2 to 20 MPa, including 5 to 15 MPa, such as 7 to 12 MPa and compressive strengths that range from 10 to 100 MPa, including 25 to 75 MPa, such as 50 MPa. Structurally reinforced concrete columns may possess considerably larger flexural strengths, ranging from 15 to 50 MPa, including 20 to 40 MPa, such as 25 to 35 MPa and compressive strengths that range from 25 to 200 MPa, including 50 to 150 MPa, such as 75 to 125 MPa. In some embodiments, columns may be composite, wherein it may act compositely with other structural units by the introduction of interfacial shear mechanisms. In other embodiments, columns may be non-composite, wherein it utilizes the properties of the basic column alone. In producing columns, the building material composition comprising sequestered-CO₂ component (e.g., component comprising carbonates, bicarbonates, or a combination thereof) may be poured into a column form or cast around a correlated steel reinforcing column structure (e.g., steel rebar). In some embodiments, the steel reinforcement is pretensioned prior to casting the composition around the steel framework. In other embodiments, columns may be cast with a steel reinforcing cage that is mechanically anchored to the concrete column. The columns may also employ additional structural support components such as, but not limited to cables, wires and mesh composed of steel, ductile iron, polymeric fibers, aluminum or plastic. The structural support components may be employed parallel, perpendicular, or at some other angle to the carried load. The molded or casted composition may be further compacted by roller compaction, hydraulic pressure, vibrational compaction, or resonant shock compaction. The composition is further allowed to set and is cured in an environment with a controlled temperature and humidity. In addition, the columns may include a variety of additional components, such as but not limited to: plasticizers, foaming agents, accelerators, retarders and air entrainment additives. Where desired, these additional components may include chemical admixtures such that the columns possess increased resistance to damage by bio-degradation, frost, water, fire and corrosion.

Another building material provided is a concrete slab. Concrete slabs are those building materials used in the construction of prefabricated foundations, floors and wall panels (e.g., landscape wall). In some instances, a concrete slab may be employed as a floor unit. (e.g., hollow plank unit or double tee design) In other instances, a precast concrete slab may be a shallow precast plank used as a foundation for in-situ concrete formwork. Wall panels are, in a broad sense, vertical load-bearing members of a building that are polygonal and possess a width that is more that four times its thickness. Precast concrete foundation, floors and wall panels may vary considerably in dimension depending on the intended use of the precast concrete slab (e.g., one or two storey building). As such, precast concrete slabs may have dimensions which range from 1 to 10 m in length or longer, including 3 to 8 m, such as 5 to 6 m; height that ranges from 1 to 10 m or taller, including 4 to 10 m, such as 4 to 5 m; and a thickness that may range from 0.005 to 0.25 m or thicker, including 0.1 to 0.2 m such as 0.1 to 0.15 m. Formed building materials such as slabs, and structures made therefrom, may be thicker than corresponding structures that lack sequestered-CO₂ components (e.g., components comprising carbonates, bicarbonates, or a combination thereof). In addition, structures made from amorphous building materials comprising sequestered-CO₂ components may be thicker than corresponding structures that lack the sequestered-CO₂ components. Such increased thickness directly relates to increased sequestered-CO₂ component content. In some embodiments, thickness of formed building materials or related structures is increased by 1.5 fold or more, 2-fold or more, or 5-fold or more. Concrete slabs may vary in their mechanical and physical properties depending on their intended use. For example, a prefabricated slab that is employed in a floor unit may possess larger flexural strengths and lesser compressive strengths than a slab that is employed as a load-bearing wall. For example, unreinforced concrete slabs may possess flexural strengths that vary, ranging from 2 to 25 MPa, including 5 to 15 MPa, such as 7 to 12 MPa and compressive strengths that range from 10 to 100 MPa, including 25 to 75 MPa, such as 50 MPa. Structurally reinforced concrete slabs may possess considerably larger flexural strengths, ranging from 15 to 50 MPa, including 20 to 40 MPa, such as 25 to 35 MPa and compressive strengths that range from 25 to 200 MPa, including 50 to 150 MPa, such as 75 to 125 MPa. In producing concrete slabs, the building material composition comprising the sequestered-CO₂ component may be poured into a slab mold or cast around a correlated steel reinforcing structure (e.g., steel rebar). In some embodiments, the steel reinforcement is pretensioned prior to casting the composition around the steel framework. In other embodiments, slabs may be cast with a steel reinforcing cage that is mechanically anchored to the concrete slab. In some embodiments, the concrete slabs may improve its structural capacity by casting a second, supportive concrete layer that is mechanically anchored to the previously precast concrete slab. The slabs may also employ additional structural support components such as, but not limited to cables, wires and mesh composed of steel, ductile iron, polymeric fibers, aluminum or plastic. The structural support components may be employed parallel, perpendicular, or at some other angle to the carried load. The molded or casted composition may be further compacted by roller compaction, hydraulic pressure, vibrational compaction, or resonant shock compaction. The composition is further allowed to set and is cured in an environment with a controlled temperature and humidity. In addition, the slabs may include a variety of further components, such as but not limited to: plasticizers, foaming agents, accelerators, retarders and air entrainment additives. Where desired, the further components may include chemical admixtures such that the slabs possess increased resistance to damage by bio-degradation, frost, water, fire and corrosion.

Another building material provided is an acoustic barrier, which refers to a structure used as a barrier for the attenuation or absorption of sound. As such, an acoustic barrier may include, but is not limited to structures such as acoustical panels, reflective barriers, absorptive barriers, reactive barriers, etc. Acoustic barriers may widely vary in size and shape. Acoustic barriers may be polygonal, circular, or any other shape depending on its intended use. Acoustic barrier may be employed in the attenuation of sound from highways, roadways, bridges, industrial facilities, power plants, loading docks, public transportation stations, military facilities, gun ranges, housing complexes, entertainment venues (e.g., stadiums, concert halls) and the like. Acoustic barriers may also be employed for sound insulation for the interior of homes, music studios, movie theaters, classrooms, etc. The acoustic barriers may have dimensions that vary greatly depending on its intended use, ranging from 0.5 to 10 m in length or longer, e.g., 5 m and 0.1 to 10 m in height/width or wider, e.g., 5 m and a thickness ranging from 10 to 100 cm, or thicker e.g., 25 to 50 cm, including 40 cm. Where desired, the acoustic barrier may be employed with various coatings or liners (e.g., polymeric), and may be configured for easy joining with each other or pillars separating additional acoustic barriers to produce long acoustic barrier structures made up of multiple acoustic barriers. In some embodiments, acoustic barriers may employ sound absorptive material (e.g., wood shavings, textile fibers, glass wool, rock wool, polymeric foam, vermiculite, etc.) in addition to a structurally reinforcing framework. In some embodiments, acoustic barriers may be used as noise-reduction barriers in an outdoor environment (e.g., along a highway, near an airport, etc.) and may be employed with structural support components (e.g., columns, posts, beams, etc.). In producing acoustic barriers, the building material composition comprising sequestered-CO₂ component (e.g., component comprising carbonates, bicarbonates, or a combination thereof) may be poured into a mold to form the desired acoustic barrier shape and size. Also the composition may be poured out into a sheet mold or a roller may be used to form sheets of a desired thickness. The shaped composition may be further compacted by roller compaction, hydraulic pressure, vibrational compaction, or resonant shock compaction. The sheets are then cut to the desired dimensions of the acoustic barriers. In some instances, the resultant composition may also be foamed using mechanically or chemically introduced gases prior to being shaped or while the composition is setting in order to form a lightweight acoustic panel structure. The shaped composition is further allowed to set and is cured in an environment with a controlled temperature and humidity. In addition, the acoustic barriers may include a variety of further components, such as but not limited to: plasticizers, foaming agents, accelerators, retarders and air entrainment additives. Where desired, the further components may include chemical admixtures such that they possess increased resistance to damage by bio-degradation, frost, water, fire and corrosion. In some embodiments, the acoustic barriers may employ structural support components such as, but not limited to cables, wires and mesh composed of steel, ductile iron, polymeric fibers, aluminum or plastic.

Another building material provided is an insulation material, which refers to a material used to attenuate or inhibit the conduction of heat. Insulation may also include those materials that reduce or inhibit radiant transmission of heat. Insulation material may consist of one or more of the following constituents: a cementitious forming material, a dispersing agent, an air entraining agent, inert densifying particulate, a mixture of ionic and non-ionic surfactants, plasticizers, accelerators, lightweight aggregate, organic and inorganic binding agents and glass particles. In certain embodiments, an amount of cementitious forming material may be replaced by the sequestered-CO₂ component (e.g., component comprising carbonates, bicarbonates, or a combination thereof) where it may be 1% by weight or more, such as 3% by weight or more, including 5% by weight or more, such as 25% by weight or more, 50% by weight or more, etc. Binding compositions for the insulation material include a component selected from the group consisting of carbides, Gypsum powder, Blakite, nitrides, calcium carbonate, oxides, titanates, sulfides, zinc selenide, zinc telluride, inorganic siloxane compound and their mixtures thereof. In certain embodiments, an amount of the binding composition may be replaced by the sequestered-CO₂ component and may be 1% by weight or more, such as 3% by weight or more, including 5% by weight or more, such as 25% by weight or more, 50% by weight or more, etc. Where desired, insulation material may also be prepared using a chemical admixture or any other convenient protocol such that they are resistant to damage by termites, insects, bacteria, fungus. etc. Insulation materials may be prepared using any convenient protocol such that they are freeze/thaw, rain and fire resistant. Insulation material may be prepared in accordance with traditional manufacturing protocols for such materials, with the exception that an amount of sequestered-CO₂ component (e.g., component comprising carbonates, bicarbonates, or a combination thereof) is employed. In producing the insulation materials, an amount of sequestered-CO₂ component) may be combined with water and other components of the insulation material, which may include, but are not limited to a dispersing agent, an air entraining agent, inert densifying particulate, a mixture of ionic and non-ionic surfactants, plasticizers, accelerators, lightweight aggregate, organic and inorganic binding agents and glass particles. The resultant insulation material may then be molded into the desired shape (e.g., wall panel) or poured into the void space of concrete masonry units, flooring units, roof decks or cast around pipes, conduits and basins.

In addition to the foregoing formed building materials, parking blocks and related parking structures (e.g., lamp post base) for parking lots are also possible. In addition, cladding-type materials may be produced, such materials including, but not limited to, window cladding, crown molding, base board, and door trim.

Preparation of Formed Building Materials

Provided herein are methods for preparing formed building materials comprising sequestered CO₂ (e.g., sequestered-CO₂ component comprising carbonates, bicarbonates, or a combination thereof). Such building materials may be prepared by first producing a sequestered-CO₂ component, and then preparing the building material from the sequestered-CO₂ component. The sequestered-CO₂ component of formed building materials described herein may be produced from a source of CO₂, a source of proton-removing agents (and/or methods of effecting proton removal), and a source of divalent cations, each of which materials are described in further detail immediately below.

Carbon Dioxide

Methods include contacting a volume of an aqueous solution of divalent cations with a source of CO₂, then subjecting the resultant solution to conditions that facilitate precipitation. Methods further include contacting a volume of an aqueous solution of divalent cations with a source of CO₂ while subjecting the aqueous solution to conditions that facilitate precipitation. There may be sufficient carbon dioxide in the divalent cation-containing solution to precipitate significant amounts of carbonate-containing precipitation material (e.g., from seawater); however, additional carbon dioxide is generally used. The source of CO₂ may be any convenient CO₂ source. The CO₂ source may be a gas, a liquid, a solid (e.g., dry ice), a supercritical fluid, or CO₂ dissolved in a liquid. In some embodiments, the CO₂ source is a gaseous CO₂ source. The gaseous stream may be substantially pure CO₂ or comprise multiple components that include CO₂ and one or more additional gases and/or other substances such as ash and other particulates. In some embodiments, the gaseous CO₂ source is a waste gas stream (i.e., a by-product of an active process of the industrial plant) such as exhaust from an industrial plant. The nature of the industrial plant may vary, the industrial plants including, but not limited to, power plants, chemical processing plants, mechanical processing plants, refineries, cement plants, steel plants, and other industrial plants that produce CO₂ as a by-product of fuel combustion or another processing step (such as calcination by a cement plant).

Waste gas streams comprising CO₂ include both reducing (e.g., syngas, shifted syngas, natural gas, hydrogen and the like) and oxidizing condition streams (e.g., flue gases from combustion). Particular waste gas streams that may be convenient include oxygen-containing combustion industrial plant flue gas (e.g., from coal or another carbon-based fuel with little or no pretreatment of the flue gas), turbo charged boiler product gas, coal gasification product gas, shifted coal gasification product gas, anaerobic digester product gas, wellhead natural gas stream, reformed natural gas or methane hydrates, and the like. Combustion gas from any convenient source may be used in methods and systems described herein. In some embodiments, combustion gases in post-combustion effluent stacks of industrial plants such as power plants, cement plants, and coal processing plants is used.

Thus, the waste streams may be produced from a variety of different types of industrial plants. Suitable waste streams include waste streams produced by industrial plants that combust fossil fuels (e.g., coal, oil, natural gas) and anthropogenic fuel products of naturally occurring organic fuel deposits (e.g., tar sands, heavy oil, oil shale, etc.). In some embodiments, a waste stream suitable for systems and methods described herein is sourced from a coal-fired power plant, such as a pulverized coal power plant, a supercritical coal power plant, a mass burn coal power plant, a fluidized bed coal power plant; in some embodiments, the waste stream is sourced from gas or oil-fired boiler and steam turbine power plants, gas or oil-fired boiler simple cycle gas turbine power plants, or gas or oil-fired boiler combined cycle gas turbine power plants. In some embodiments, waste streams produced by power plants that combust syngas (i.e., gas that is produced by the gasification of organic matter, for example, coal, biomass, etc.) are used. In some embodiments, waste streams from integrated gasification combined cycle (IGCC) plants are used. In some embodiments, waste streams produced by Heat Recovery Steam Generator (HRSG) plants are used in accordance with systems and methods described herein.

Waste streams produced by cement plants are also suitable for systems and methods described herein. Cement plant waste streams include waste streams from both wet process and dry process plants, which plants may employ shaft kilns or rotary kilns, and may include pre-calciners. These industrial plants may each burn a single fuel, or may burn two or more fuels sequentially or simultaneously. Other industrial plants such as smelters and refineries are also useful sources of waste streams that include carbon dioxide.

Industrial waste gas streams may contain carbon dioxide as the primary non-air derived component, or may, especially in the case of coal-fired power plants, contain additional components such as nitrogen oxides (NOx), sulfur oxides (SOx), and one or more additional gases. Additional gases and other components may include CO, mercury and other heavy metals, and dust particles (e.g., from calcining and combustion processes). Additional components in the gas stream may also include halides such as hydrogen chloride and hydrogen fluoride; particulate matter such as fly ash, dusts, and metals including arsenic, beryllium, boron, cadmium, chromium, chromium VI, cobalt, lead, manganese, mercury, molybdenum, selenium, strontium, thallium, and vanadium; and organics such as hydrocarbons, dioxins, and PAH compounds. Suitable gaseous waste streams that may be treated have, in some embodiments, CO₂ present in amounts of 200 ppm to 1,000,000 ppm, such as 200,000 ppm to 1000 ppm, including 200,000 ppm to 2000 ppm, for example 180,000 ppm to 2000 ppm, or 180,000 ppm to 5000 ppm, also including 180,000 ppm to 10,000 ppm. The waste streams, particularly various waste streams of combustion gas, may include one or more additional components, for example, water, NOx (mononitrogen oxides: NO and NO₂), SOx (monosulfur oxides: SO, SO₂ and SO₃), VOC (volatile organic compounds), heavy metals such as mercury, and particulate matter (particles of solid or liquid suspended in a gas). Flue gas temperature may also vary. In some embodiments, the temperature of the flue gas comprising CO₂ is from 0° C. to 2000° C., such as from 60° C. to 700° C., and including 100° C. to 400° C.

In some embodiments, one or more additional components or co-products (i.e., products produced from other starting materials [e.g., SOx, NOx, etc.] under the same conditions employed to convert CO₂ into carbonates) are precipitated or trapped in precipitation material formed by contacting the waste gas stream comprising these additional components with an aqueous solution comprising divalent cations (e.g., alkaline earth metal ions such as Ca²⁺ and Mg²⁺). Sulfates, sulfites, and the like of calcium and/or magnesium may be precipitated or trapped in precipitation material (further comprising calcium and/or magnesium carbonates) produced from waste gas streams comprising SOx (e.g., SO₂). Magnesium and calcium may react to form MgSO₄, CaSO₄, respectively, as well as other magnesium-containing and calcium-containing compounds (e.g., sulfites), effectively removing sulfur from the flue gas stream without a desulfurization step such as flue gas desulfurization (“FGD”). In addition, CaCO₃, MgCO₃, and related compounds may be formed without additional release of CO₂. In instances where the aqueous solution of divalent cations contains high levels of sulfur compounds (e.g., sulfate), the aqueous solution may be enriched with calcium and magnesium so that calcium and magnesium are available to form carbonate compounds after, or in addition to, formation of CaSO₄, MgSO₄, and related compounds. In some embodiments, a desulfurization step may be staged to coincide with precipitation of carbonate-containing precipitation material, or the desulfurization step may be staged to occur before precipitation. In some embodiments, multiple reaction products (e.g., MgCO₃, CaCO₃, CaSO₄, mixtures of the foregoing, and the like) are collected at different stages, while in other embodiments a single reaction product (e.g., precipitation material comprising carbonates, sulfates, etc.) is collected. In step with these embodiments, other components, such as heavy metals (e.g., mercury, mercury salts, mercury-containing compounds), may be trapped in the carbonate-containing precipitation material or may precipitate separately.

A portion of the gaseous waste stream (i.e., not the entire gaseous waste stream) from an industrial plant may be used to produce precipitation material. In these embodiments, the portion of the gaseous waste stream that is employed in precipitation of precipitation material may be 75% or less, such as 60% or less, and including 50% and less of the gaseous waste stream. In yet other embodiments, substantially (e.g., 80% or more) the entire gaseous waste stream produced by the industrial plant is employed in precipitation of precipitation material. In these embodiments, 80% or more, such as 90% or more, including 95% or more, up to 100% of the gaseous waste stream (e.g., flue gas) generated by the source may be employed for precipitation of precipitation material.

Although industrial waste gas offers a relatively concentrated source of combustion gases, methods and systems provided herein are also applicable to removing combustion gas components from less concentrated sources (e.g., atmospheric air), which contains a much lower concentration of pollutants than, for example, flue gas. Thus, in some embodiments, methods and systems encompass decreasing the concentration of pollutants in atmospheric air by producing a stable precipitation material. In these cases, the concentration of pollutants, e.g., CO₂, in a portion of atmospheric air may be decreased by 10% or more, 20% or more, 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, 95% or more, 99% or more, 99.9% or more, or 99.99%. Such decreases in atmospheric pollutants may be accomplished with yields as described herein, or with higher or lower yields, and may be accomplished in one precipitation step or in a series of precipitation steps.

Divalent Cations

Methods include contacting a volume of an aqueous solution of divalent cations with a source of CO₂ and subjecting the resultant solution to conditions that facilitate precipitation. In some embodiments, a volume of an aqueous solution of divalent cations is contacted with a source of CO₂ while subjecting the aqueous solution to conditions that facilitate precipitation. Divalent cations may come from any of a number of different divalent cation sources depending upon availability at a particular location. Such sources include industrial wastes, seawater, brines, hard waters, rocks and minerals (e.g., lime, periclase, material comprising metal silicates such as serpentine and olivine), and any other suitable source.

In some locations, industrial waste streams from various industrial processes provide for convenient sources of divalent cations (as well as in some cases other materials useful in the process, e.g., metal hydroxide). Such waste streams include, but are not limited to, mining wastes; fossil fuel burning ash (e.g., combustion ash such as fly ash, bottom ash, boiler slag); slag (e.g. iron slag, phosphorous slag); cement kiln waste; oil refinery/petrochemical refinery waste (e.g. oil field and methane seam brines); coal seam wastes (e.g. gas production brines and coal seam brine); paper processing waste; water softening waste brine (e.g., ion exchange effluent); silicon processing wastes; agricultural waste; metal finishing waste; high pH textile waste; and caustic sludge. Fossil fuel burning ash, cement kiln dust, and slag, collectively waste sources of metal oxides, further described in U.S. patent application Ser. No. 12/486,692, filed 17 Jun. 2009, the disclosure of which is incorporated herein in its entirety. Any of the divalent cation sources described herein may be mixed and matched. For example, material comprising metal silicates (e.g. serpentine, olivine), which are further described in U.S. patent application Ser. No. 12/501,217, filed 10 Jul. 2009, which application is herein incorporated by reference, may be combined with any of the sources of divalent cations described herein.

In some locations, a convenient source of divalent cations for preparation of a precipitation material (e.g., carbonates, bicarbonates, or a combination thereof) is water (e.g., an aqueous solution comprising divalent cations such as seawater or surface brine), which may vary depending upon the particular location from which the water is sourced. Suitable aqueous solutions of divalent cations that may be used include solutions comprising one or more divalent cations, e.g., alkaline earth metal cations such as Ca²⁺ and Mg²⁺. In some embodiments, the aqueous source of divalent cations comprises alkaline earth metal cations. In some embodiments, the alkaline earth metal cations include calcium, magnesium, or a mixture thereof. In some embodiments, the aqueous solution of divalent cations comprises calcium in amounts ranging from 50 to 50,000 ppm, 50 to 40,000 ppm, 50 to 20,000 ppm, 100 to 10,000 ppm, 200 to 5000 ppm, or 400 to 1000 ppm. In some embodiments, the aqueous solution of divalent cations comprises magnesium in amounts ranging from 50 to 40,000 ppm, 50 to 20,000 ppm, 100 to 10,000 ppm, 200 to 10,000 ppm, 500 to 5000 ppm, or 500 to 2500 ppm. In some embodiments, where Ca² and Mg²⁺ are both present, the ratio of Ca²⁺ to Mg²⁺ (i.e., Ca²⁺:Mg²⁺) in the aqueous solution of divalent cations is between 1:1 and 1:2.5; 1:2.5 and 1:5; 1:5 and 1:10; 1:10 and 1:25; 1:25 and 1:50; 1:50 and 1:100; 1:100 and 1:150; 1:150 and 1:200; 1:200 and 1:250; 1:250 and 1:500; 1:500 and 1:1000, or a range thereof. For example, in some embodiments, the ratio of Ca²⁺ to Mg²⁺ in the aqueous solution of divalent cations is between 1:1 and 1:10; 1:5 and 1:25; 1:10 and 1:50; 1:25 and 1:100; 1:50 and 1:500; or 1:100 and 1:1000. In some embodiments, the ratio of Mg²⁺ to Ca²⁺ (i.e., Mg²⁺:Ca²) in the aqueous solution of divalent cations is between 1:1 and 1:2.5; 1:2.5 and 1:5; 1:5 and 1:10; 1:10 and 1:25; 1:25 and 1:50; 1:50 and 1:100; 1:100 and 1:150; 1:150 and 1:200; 1:200 and 1:250; 1:250 and 1:500; 1:500 and 1:1000, or a range thereof. For example, in some embodiments, the ratio of Mg²⁺ to Ca²⁺ in the aqueous solution of divalent cations is between 1:1 and 1:10; 1:5 and 1:25; 1:10 and 1:50; 1:25 and 1:100; 1:50 and 1:500; or 1:100 and 1:1000.

The aqueous solution of divalent cations may comprise divalent cations derived from freshwater, brackish water, seawater, or brine (e.g., naturally occurring brines or anthropogenic brines such as geothermal plant wastewaters, desalination plant waste waters), as well as other salines having a salinity that is greater than that of freshwater, any of which may be naturally occurring or anthropogenic. Brackish water is water that is saltier than freshwater, but not as salty as seawater. Brackish water has a salinity ranging from about 0.5 to about 35 ppt (parts per thousand). Seawater is water from a sea, an ocean, or any other saline body of water that has a salinity ranging from about 35 to about 50 ppt. Brine is water saturated or nearly saturated with salt. Brine has a salinity that is about 50 ppt or greater. In some embodiments, the water source from which divalent cations are derived is a mineral rich (e.g., calcium-rich and/or magnesium-rich) freshwater source. In some embodiments, the water source from which divalent cations are derived is a naturally occurring saltwater source selected from a sea, an ocean, a lake, a swamp, an estuary, a lagoon, a surface brine, a deep brine, an alkaline lake, an inland sea, or the like. In some embodiments, the water source from which divalent cation are derived is an anthropogenic brine selected from a geothermal plant wastewater or a desalination wastewater.

Freshwater is often a convenient source of divalent cations (e.g., cations of alkaline earth metals such as Ca²⁺ and Mg²⁺). Any of a number of suitable freshwater sources may be used, including freshwater sources ranging from sources relatively free of minerals to sources relatively rich in minerals. Mineral-rich freshwater sources may be naturally occurring, including any of a number of hard water sources, lakes, or inland seas. Some mineral-rich freshwater sources such as alkaline lakes or inland seas (e.g., Lake Van in Turkey) also provide a source of pH-modifying agents. Mineral-rich freshwater sources may also be anthropogenic. For example, a mineral-poor (soft) water may be contacted with a source of divalent cations such as alkaline earth metal cations (e.g., Ca²⁺, Mg²⁺, etc.) to produce a mineral-rich water that is suitable for methods and systems described herein. Divalent cations or precursors thereof (e.g. salts, minerals) may be added to freshwater (or any other type of water described herein) using any convenient protocol (e.g., addition of solids, suspensions, or solutions). In some embodiments, divalent cations selected from Ca²⁺ and Mg²⁺ are added to freshwater. In some embodiments, monovalent cations selected from Na+ and K+ are added to freshwater. In some embodiments, freshwater comprising Ca²⁺ is combined with combustion ash (e.g., fly ash, bottom ash, boiler slag), or products or processed forms thereof, yielding a solution comprising calcium and magnesium cations.

In some embodiments, an aqueous solution of divalent cations may be obtained from an industrial plant that is also providing a combustion gas stream. For example, in water-cooled industrial plants, such as seawater-cooled industrial plants, water that has been used by an industrial plant for cooling may then be used as water for producing precipitation material. If desired, the water may be cooled prior to entering a precipitation system. Such approaches may be employed, for example, with once-through cooling systems. For example, a city or agricultural water supply may be employed as a once-through cooling system for an industrial plant. Water from the industrial plant may then be employed for producing precipitation material, wherein output water has a reduced hardness and greater purity.

Proton-Removing Agents and Methods for Effecting Proton Removal

Methods include contacting a volume of an aqueous solution of divalent cations with a source of CO₂ (to dissolve CO₂) and subjecting the resultant solution to conditions that facilitate precipitation. In some embodiments, a volume of an aqueous solution of divalent cations is contacted with a source of CO₂ (to dissolve CO₂) while subjecting the aqueous solution to conditions that facilitate precipitation. The dissolution of CO₂ into the aqueous solution of divalent cations produces carbonic acid, a species in equilibrium with both bicarbonate and carbonate. In order to produce carbonate-containing precipitation material, protons are removed from various species (e.g. carbonic acid, bicarbonate, hydronium, etc.) in the divalent cation-containing solution to shift the equilibrium toward carbonate. As protons are removed, more CO₂ goes into solution. In some embodiments, proton-removing agents and/or methods are used while contacting a divalent cation-containing aqueous solution with CO₂ to increase CO₂ absorption in one phase of the precipitation reaction, wherein the pH may remain constant, increase, or even decrease, followed by a rapid removal of protons (e.g., by addition of a base) to cause rapid precipitation of carbonate-containing precipitation material. Protons may be removed from the various species (e.g. carbonic acid, bicarbonate, hydronium, etc.) by any convenient approach, including, but not limited to use of naturally occurring proton-removing agents, use of microorganisms and fungi, use of synthetic chemical proton-removing agents, recovery of man-made waste streams, and using electrochemical means.

Naturally occurring proton-removing agents encompass any proton-removing agents that can be found in the wider environment that may create or have a basic local environment. Some embodiments provide for naturally occurring proton-removing agents including minerals that create basic environments upon addition to solution. Such minerals include, but are not limited to, lime (CaO); periclase (MgO); iron hydroxide minerals (e.g., goethite and limonite); and volcanic ash. Methods for digestion of such minerals and rocks comprising such minerals are provided herein. Some embodiments provide for using naturally alkaline bodies of water as naturally occurring proton-removing agents. Examples of naturally alkaline bodies of water include, but are not limited to surface water sources (e.g. alkaline lakes such as Mono Lake in California) and ground water sources (e.g. basic aquifers such as the deep geologic alkaline aquifers located at Searles Lake in California). Other embodiments provide for use of deposits from dried alkaline bodies of water such as the crust along Lake Natron in Africa's Great Rift Valley. In some embodiments, organisms that excrete basic molecules or solutions in their normal metabolism are used as proton-removing agents. Examples of such organisms are fungi that produce alkaline protease (e.g., the deep-sea fungus Aspergillus ustus with an optimal pH of 9) and bacteria that create alkaline molecules (e.g., cyanobacteria such as Lyngbya sp. from the Atlin wetland in British Columbia, which increases pH from a byproduct of photosynthesis). In some embodiments, organisms are used to produce proton-removing agents, wherein the organisms (e.g., Bacillus pasteurii, which hydrolyzes urea to ammonia) metabolize a contaminant (e.g. urea) to produce proton-removing agents or solutions comprising proton-removing agents (e.g., ammonia, ammonium hydroxide). In some embodiments, organisms are cultured separately from the precipitation reaction mixture, wherein proton-removing agents or solution comprising proton-removing agents are used for addition to the precipitation reaction mixture. In some embodiments, naturally occurring or manufactured enzymes are used in combination with proton-removing agents to invoke precipitation of precipitation material. Carbonic anhydrase, which is an enzyme produced by plants and animals, accelerates transformation of carbonic acid to bicarbonate in aqueous solution. As such, carbonic anhydrase may be used to enhance dissolution of CO₂ and accelerate precipitation of precipitation material.

Chemical agents for effecting proton removal generally refer to synthetic chemical agents that are produced in large quantities and are commercially available. For example, chemical agents for removing protons include, but are not limited to, hydroxides, organic bases, super bases, oxides, ammonia, and carbonates. Hydroxides include chemical species that provide hydroxide anions in solution, including, for example, sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca(OH)₂), or magnesium hydroxide (Mg(OH)₂). Organic bases are carbon-containing molecules that are generally nitrogenous bases including primary amines such as methyl amine, secondary amines such as diisopropylamine, tertiary such as diisopropylethylamine, aromatic amines such as aniline, heteroaromatics such as pyridine, imidazole, and benzimidazole, and various forms thereof. In some embodiments, an organic base selected from pyridine, methylamine, imidazole, benzimidazole, histidine, and a phosphazene is used to remove protons from various species (e.g., carbonic acid, bicarbonate, hydronium, etc.) for precipitation of precipitation material. In some embodiments, ammonia is used to raise pH to a level sufficient to precipitate precipitation material from a solution of divalent cations and an industrial waste stream. Super bases suitable for use as proton-removing agents include sodium ethoxide, sodium amide (NaNH₂), sodium hydride (NaH), butyl lithium, lithium diisopropylamide, lithium diethylamide, and lithium bis(trimethylsilyl)amide. Oxides including, for example, calcium oxide (CaO), magnesium oxide (MgO), strontium oxide (SrO), beryllium oxide (BeO), and barium oxide (BaO) are also suitable proton-removing agents that may be used. Carbonates include, but are not limited to, sodium carbonate and potassium carbonate.

In addition to comprising cations of interest and other suitable metal forms, waste streams from various industrial processes may provide proton-removing agents. Such waste streams include, but are not limited to, mining wastes; fossil fuel burning ash (e.g., combustion ash such as fly ash, bottom ash, boiler slag); slag (e.g. iron slag, phosphorous slag); cement kiln waste; oil refinery/petrochemical refinery waste (e.g. oil field and methane seam brines); coal seam wastes (e.g. gas production brines and coal seam brine); paper processing waste; water softening waste brine (e.g., ion exchange effluent); silicon processing wastes; agricultural waste; metal finishing waste; high pH textile waste; and caustic sludge. Mining wastes include any wastes from the extraction of metal or another precious or useful mineral from the earth. In some embodiments, wastes from mining are used to modify pH, wherein the waste is selected from red mud from the Bayer aluminum extraction process; waste from magnesium extraction from seawater (e.g., Mg(OH)₂ such as that found in Moss Landing, Calif.); and wastes from mining processes involving leaching. For example, red mud may be used to modify pH as described in U.S. Provisional Patent Application No. 61/161,369, filed 18 Mar. 2009, which is incorporated herein by reference in its entirety. Fossil fuel burning ash, cement kiln dust, and slag, collectively waste sources of metal oxides, further described in U.S. patent application Ser. No. 12/486,692, filed 17 Jun. 2009, the disclosure of which is incorporated herein in its entirety, may be used alone or in combination with other proton-removing agents to provide proton-removing agents. Agricultural waste, either through animal waste or excessive fertilizer use, may contain potassium hydroxide (KOH) or ammonia (NH₃) or both. As such, agricultural waste may be used in some embodiments as a proton-removing agent. This agricultural waste is often collected in ponds, but it may also percolate down into aquifers, where it can be accessed and used.

Electrochemical methods are another means to remove protons from various species in a solution, either by removing protons from solute (e.g., deprotonation of carbonic acid or bicarbonate) or from solvent (e.g., deprotonation of hydronium or water). Deprotonation of solvent may result, for example, if proton production from CO₂ dissolution matches or exceeds electrochemical proton removal from solute molecules. In some embodiments, low-voltage electrochemical methods are used to remove protons, for example, as CO₂ is dissolved in the precipitation reaction mixture or a precursor solution to the precipitation reaction mixture (i.e., a solution that may or may not contain divalent cations). In some embodiments, CO₂ dissolved in an aqueous solution that does not contain divalent cations is treated by a low-voltage electrochemical method to remove protons from carbonic acid, bicarbonate, hydronium, or any species or combination thereof resulting from the dissolution of CO₂. A low-voltage electrochemical method operates at an average voltage of 2, 1.9, 1.8, 1.7, or 1.6 V or less, such as 1.5, 1.4, 1.3, 1.2, 1.1 V or less, such as 1 V or less, such as 0.9 V or less, 0.8 V or less, 0.7 V or less, 0.6 V or less, 0.5 V or less, 0.4 V or less, 0.3 V or less, 0.2 V or less, or 0.1 V or less. Low-voltage electrochemical methods that do not generate chlorine gas are convenient for use in systems and methods described herein. Low-voltage electrochemical methods to remove protons that do not generate oxygen gas are also convenient for use in systems and methods described herein. In some embodiments, low-voltage electrochemical methods generate hydrogen gas at the cathode and transport it to the anode where the hydrogen gas is converted to protons. Electrochemical methods that do not generate hydrogen gas may also be convenient. In some instances, electrochemical methods to remove protons do not generate any gaseous by-byproduct. Electrochemical methods for effecting proton removal are further described in U.S. patent application Ser. No. 12/344,019, filed 24 Dec. 2008; U.S. patent application Ser. No. 12/375,632, filed 23 Dec. 2008; International Patent Application No. PCT/US08/088242, filed 23 Dec. 2008; International Patent Application No. PCT/US09/32301, filed 28 Jan. 2009; and International Patent Application No. PCT/US09/48511, filed 24 Jun. 2009, each of which are incorporated herein by reference in their entirety.

Alternatively, electrochemical methods may be used to produce caustic molecules (e.g., hydroxide) through, for example, the chlor-alkali process, or modification thereof. Electrodes (i.e., cathodes and anodes) may be present in the apparatus containing the divalent cation-containing aqueous solution or gaseous waste stream-charged (e.g., CO₂-charged) solution, and a selective barrier, such as a membrane, may separate the electrodes. Electrochemical systems and methods for removing protons may produce by-products (e.g., hydrogen) that may be harvested and used for other purposes. Additional electrochemical approaches that may be used in systems and methods described herein include, but are not limited to, those described in U.S. Provisional Patent Application No. 61/081,299, filed 16 Jul. 2008, and U.S. Provisional Patent Application No. 61/091,729, the disclosures of which are incorporated herein by reference. Combinations of the above mentioned sources of proton-removing agents and methods for effecting proton removal may be employed.

Preparation of Sequestered-CO₂ Components and Building Materials Therefrom

A variety of different methods may be employed to prepare the CO₂-sequestrating component from the source of CO₂, the source of divalent cations, and the source of proton-removing agents. CO₂ sequestration protocols of interest include, but are not limited to, those disclosed in U.S. patent application Ser. No. 12/126,776, filed 23 May 2008; Ser. No. 12/163,205, filed 27 Jun. 2008; Ser. No. 12/344,019, filed 24 Dec. 2008; and Ser. No. 12/475,378, filed 29 May 2009, as well as U.S. Provisional Patent Application Ser. Nos. 61/017,405, filed 28 Dec. 2007; 61/017,419, filed 28 Dec. 2007; 61/057,173, filed 29 May 2008; 61/056,972, filed 29 May 2008; 61/073,319, filed 17 Jun. 2008; 61/079,790, 10 Jul. 2008; 61/081,299, filed 16 Jul. 2008; 61/082,766, filed 22 Jul. 2008; 61/088,347, filed 13 Aug. 2008; 61/088,340, filed 12 Aug. 2008; 61/101,629, filed 30 Sep. 2008; and 61/101,631, filed 30 Sep. 2008; the disclosures of which are incorporated herein by reference.

Sequestered-CO₂ components include compositions comprising carbonates, bicarbonates, and combinations thereof that may be produced by precipitation from a solution of divalent cations such as calcium and/or magnesium. The carbonate compound compositions include precipitated crystalline and/or amorphous carbonate compounds. The carbonates, bicarbonates, and combinations thereof that make up the sequestered-CO₂ components include metastable carbonate compounds that may be precipitated from a solution of divalent cations, such as a saltwater, as described in greater detail below. For convenience, the description provided herein is sometimes given in terms of saltwater; however, it is to be understood that any source of water comprising divalent cations may be used.

Saltwater-derived carbonate compound compositions (i.e., compositions derived from saltwater and made up of one or more different carbonate crystalline and/or amorphous compounds with or without one or more hydroxide crystalline or amorphous compounds) are ones that are derived from a saltwater. As such, they are compositions that are obtained from a saltwater in some manner, e.g., by treating a volume of a saltwater in a manner sufficient to produce the desired carbonate compound composition from the initial volume of saltwater. The carbonate compound compositions of certain embodiments are produced by precipitation from a solution of divalent cations (e.g., a saltwater) that includes alkaline earth metal cations, such as calcium and magnesium, etc., where such solutions of divalent cations may be collectively referred to as alkaline earth metal-containing waters.

The saltwater employed in methods may vary. As reviewed above, saltwater of interest include brackish water, seawater and brine, as well as other salines having a salinity that is greater than that of freshwater (which has a salinity of less than 5 ppt dissolved salts). In some embodiments, calcium rich waters may be combined with magnesium silicate minerals, such as olivine or serpentine, in solution that has become acidic due to the addition on carbon dioxide to form carbonic acid, which dissolves the magnesium silicate, leading to the formation of calcium magnesium silicate carbonate compounds as mentioned above.

In methods of producing the carbonate compound compositions, a volume of water is subjected to carbonate compound precipitation conditions sufficient to produce a carbonate-containing precipitation material and a mother liquor (i.e., the part of the water that is left over after precipitation of the carbonate compound(s) from the saltwater). The resultant precipitation material and mother liquor collectively make up the carbonate compound compositions. Any convenient precipitation conditions may be employed, which conditions result in the production of a carbonate compound composition sequestration product.

Conditions that facilitate precipitation (i.e., precipitation conditions) may vary. For example, the temperature of the water may be within a suitable range for the precipitation of the desired mineral to occur. In some embodiments, the temperature of the water may be in a range from 5 to 70° C., such as from 20 to 50° C. and including from 25 to 45° C. As such, while a given set of precipitation conditions may have a temperature ranging from 0 to 100° C., the temperature of the water may have to be adjusted in certain embodiments to produce the desired precipitation material.

In normal seawater, 93% of the dissolved CO₂ is in the form of bicarbonate ions (HCO₃ ⁻) and 6% is in the form of carbonate ions (CO₃ ²⁻). When calcium carbonate precipitates from normal seawater, CO₂ is released. In fresh water, above pH 10.33, greater than 90% of the carbonate is in the form of carbonate ion, and no CO₂ is released during the precipitation of calcium carbonate. In seawater this transition occurs at a slightly lower pH, closer to a pH of 9.7. While the pH of the water employed in methods may range from 5 to 14 during a given precipitation process, in certain embodiments the pH is raised to alkaline levels in order to drive the precipitation of carbonate compounds, as well as other compounds, e.g., hydroxide compounds, as desired. In certain of these embodiments, the pH is raised to a level that minimizes if not eliminates CO₂ production during precipitation, causing dissolved CO₂, e.g., in the form of carbonate and bicarbonate, to be trapped in the precipitation material. In these embodiments, the pH may be raised to 10 or higher, such as 11 or higher.

The pH of the water may be raised using any convenient approach. In certain embodiments, a proton-removing agent is employed, where examples of such agents include oxides, hydroxides (e.g., calcium oxide in fly ash, potassium hydroxide, sodium hydroxide, brucite (Mg(OH₂), etc.), carbonates (e.g., sodium carbonate), and the like, many of which are described above. One such approach for raising the pH of the precipitation reaction mixture or precursor thereof (e.g., divalent cation-containing solution) is to use the coal ash from a coal-fired power plant, which contains many oxides. Other coal processes, like the gasification of coal, to produce syngas, also produce hydrogen gas and carbon monoxide, and may serve as a source of hydroxide as well. Some naturally occurring minerals, such as serpentine, contain hydroxide and may be dissolved to yield a source of hydroxide. The addition of serpentine also releases silica and magnesium into the solution, leading to the formation of silica-containing precipitation material. The amount of proton-removing agent that is added to the precipitation reaction mixture or precursor thereof will depend on the particular nature of the proton-removing agent and the volume of the precipitation reaction mixture or precursor thereof being modified, and will be sufficient to raise the pH of the precipitation reaction mixture or precursor thereof to the desired pH. Alternatively, the pH of the precipitation reaction mixture or precursor thereof may be raised to the desired level by electrochemical means as described above. Additional electrochemical methods may be used under certain conditions. For example, electrolysis may be employed, wherein the mercury cell process (also called the Castner-Kellner process); the diaphragm cell process, the membrane cell process, or some combination thereof is used. Where desired, byproducts of the hydrolysis product, e.g., H₂, sodium metal, etc. may be harvested and employed for other purposes, as desired. In yet other embodiments, the pH-elevating approach described in U.S. Provisional Patent Application Nos. 61/081,299, filed 16 Jul. 2008, and 61/091,729, filed 25 Aug. 2008, may be employed, the disclosures of which are incorporated herein by reference.

Additives other than pH-elevating agents may also be introduced into the water in order to influence the nature of the precipitation material that is produced. As such, certain embodiments of the methods include providing an additive in water before or during the time when the water is subjected to the precipitation conditions. Certain calcium carbonate polymorphs can be favored by trace amounts of certain additives. For example, vaterite, a highly unstable polymorph of CaCO₃, which precipitates in a variety of different morphologies and converts rapidly to calcite, can be obtained at very high yields by including trace amounts of lanthanum as lanthanum chloride in a supersaturated solution of calcium carbonate. Other additives beside lanthanum that are of interest include, but are not limited to transition metals and the like. For instance, the addition of ferrous or ferric iron is known to favor the formation of disordered dolomite (protodolomite) where it would not form otherwise.

The nature of the precipitation material can also be influenced by selection of appropriate major ion ratios. Major ion ratios also have considerable influence of polymorph formation. For example, as the magnesium:calcium ratio in the water increases, aragonite becomes the favored polymorph of calcium carbonate over low-magnesium calcite. At low magnesium:calcium ratios, low-magnesium calcite is the preferred polymorph. As such, a wide range of magnesium:calcium ratios can be employed, including, for example, 100:1, 50:1, 20:1, 10:1, 5:1, 2:1, 1:1, 1:2, 1:5, 1:10, 1:20, 1:50, 1:100, or any of the ratios mentioned above. In certain embodiments, the magnesium:calcium ratio is determined by the source of water employed in the precipitation process (e.g., seawater, brine, brackish water, fresh water), whereas in other embodiments, the magnesium:calcium ratio is adjusted to fall within a certain range.

Rate of precipitation also has a large effect on compound phase formation. The most rapid precipitation can be achieved by seeding the solution with a desired phase. Without seeding, rapid precipitation can be achieved by rapidly increasing the pH of the seawater, which results in more amorphous constituents. When silica is present, the more rapid the reaction rate, the more silica is incorporated in the carbonate-containing precipitation material. The higher the pH is, the more rapid the precipitation is and the more amorphous the precipitation material.

Accordingly, a set of precipitation conditions to produce a desired precipitation material from a solution of divalent cations includes, in certain embodiments, the water's temperature and pH, and in some instances, the concentrations of additives and ionic species in the water. Precipitation conditions may also include factors such as mixing rate, forms of agitation such as ultrasonics, and the presence of seed crystals, catalysts, membranes, or substrates. In some embodiments, precipitation conditions include supersaturated conditions, temperature, pH, and/or concentration gradients, or cycling or changing any of these parameters. The protocols employed to prepare carbonate-containing precipitation material may be batch or continuous protocols. It will be appreciated that precipitation conditions may be different to produce a given precipitation material in a continuous flow system compared to a batch system.

In certain embodiments, the methods further include contacting the volume of water that is subjected to the mineral precipitation conditions with a source of CO₂. Contact of the water with the source CO₂ may occur before and/or during the time when the water is subjected to CO₂ precipitation conditions. Accordingly, embodiments include methods in which the volume of water is contacted with a source of CO₂ prior to subjecting the volume of saltwater to mineral precipitation conditions. Embodiments include methods in which the volume of saltwater is contacted with a source of CO₂ while the volume of saltwater is being subjected to carbonate compound precipitation conditions. Embodiments include methods in which the volume of water is contacted with a source of a CO₂ both prior to subjecting the volume of saltwater to carbonate compound precipitation conditions and while the volume of saltwater is being subjected to carbonate compound precipitation conditions. In some embodiments, the same water may be cycled more than once, wherein a first cycle of precipitation removes primarily calcium carbonate and magnesium carbonate minerals, and leaves remaining alkaline water to which other alkaline earth ion sources may be added, that can have more carbon dioxide cycled through it, precipitating more carbonate compounds.

The source of CO₂ that is contacted with the volume of saltwater in these embodiments may be any convenient CO₂ source, and the contact protocol may be any convenient protocol. Where the CO₂ is a gas, contact protocols of interest include, but are not limited to: direct contacting protocols, e.g., bubbling the gas through the volume of saltwater, concurrent contacting means, i.e., contact between unidirectionally flowing gaseous and liquid phase streams, countercurrent means, i.e., contact between oppositely flowing gaseous and liquid phase streams, and the like. Thus, contact may be accomplished through use of infusers, bubblers, fluidic Venturi reactor, sparger, gas filter, spray, tray, or packed column reactors, and the like, as may be convenient. For exemplary system and methods for contacting the solution of divalent cations with the source of CO2, see U.S. Provisional Patent Application Nos. 61/158,992, filed 10 Mar. 2009; 61/168,166, filed 9 Apr. 2009; 61/170,086, filed 16 Apr. 2009; 61/178,475, filed 14 May 2009; 61/228,210, filed 24 Jul. 2009; 61/230,042, filed 30 Jul. 2009; and 61/239,429, filed 2 Sep. 2009, each of which is incorporated herein by reference.

The above protocol results in the production of a slurry composition comprising precipitation material comprising carbonates, bicarbonates, or a combination thereof, and a mother liquor. Where desired, the compositions made up of the precipitation material and the mother liquor may be stored for a period of time following precipitation and prior to further processing. For example, the composition may be stored for a period of time ranging from 1 to 1000 days or longer, such as 1 to 10 days or longer, at a temperature ranging from 1 to 40° C., such as 20 to 25° C.

The slurry components are then separated. Embodiments may include treatment of the mother liquor, where the mother liquor may or may not be present in the same composition as the product. For example, where the mother liquor is to be returned to the ocean, the mother liquor may be contacted with a gaseous source of CO₂ in a manner sufficient to increase the concentration of carbonate ion present in the mother liquor. Contact may be conducted using any convenient protocol, such as those described above. In certain embodiments, the mother liquor has an alkaline pH, and contact with the CO₂ source is carried out in a manner sufficient to reduce the pH to a range between 5 and 9, e.g., 6 and 8.5, including 7.5 to 8.2. In certain embodiments, the treated brine may be contacted with a source of CO₂, e.g., as described above, to sequester further CO₂. For example, where the mother liquor is to be returned to the ocean, the mother liquor may be contacted with a gaseous source of CO₂ in a manner sufficient to increase the concentration of carbonate ion present in the mother liquor. Contact may be conducted using any convenient protocol, such as those described above. In certain embodiments, the mother liquor has an alkaline pH, and contact with the CO₂ source is carried out in a manner sufficient to reduce the pH to a range between 5 and 9, e.g., 6 and 8.5, including 7.5 to 8.2.

The resultant mother liquor of the reaction may be disposed of using any convenient protocol. In certain embodiments, it may be sent to a tailings pond for disposal. In certain embodiments, it may be disposed of in a naturally occurring body of water, e.g., ocean, sea, lake or river. In certain embodiments, the mother liquor is returned to the source of feed water (e.g., an ocean, a sea, etc.). Alternatively, the mother liquor may be further processed, e.g., subjected to desalination protocols, as described further in U.S. application Ser. No. 12/163,205; the disclosure of which is herein incorporated by reference.

In certain embodiments, following production of the precipitation material (e.g., composition comprising carbonates, bicarbonates, or combinations thereof), the precipitation material may be separated from the mother liquor to produce separated precipitation material. Separation of the precipitation material from the mother liquor may be achieved using any convenient approach, including draining mother liquor (or supernatant) from the precipitation material, either by gravity alone or with the addition of a vacuum; mechanical pressing; filtering the precipitation material from the mother liquor to produce a filtrate; etc. Separation of bulk water produces, in certain embodiments, a wet, dewatered precipitation material. Dewatered precipitation material may comprise at least 1%, 5%, 10%, 15%, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 60%, 62%, 64%, 66%, 68%, 70%, 72%, 74%, 76%, 78%, 80%, 82%, 84%, 86%, 88%, or 90% (w/w) or (w/v) solids (e.g. carbonates, bicarbonates, or a combination of carbonates and bicarbonates). Dewatered precipitation material may comprise less than 90%, 88%, 86%, 84%, 82%, 80%, 78%, 76%, 74%, 72%, 70%, 68%, 66%, 64%, 62%, 60%, 58%, 56%, 54%, 52%, 50%, 48%, 46%, 44%, 42%, 40%, 38%, 36%, 34%, 32%, 30%, 28%, 26%, 24%, 22%, 20%, 15%, 10%, 5%, or 1% (w/w) or (w/v) solids (e.g., carbonates, bicarbonates, or a combination of carbonates and bicarbonates). Combinations of the foregoing may also be used to dewatered precipitation material. For example, in some embodiments, dewatered precipitation material, which is a concentrated composition of precipitation material, concentrated with respect to carbonates, bicarbonates, or carbonates and bicarbonates, may comprise at least 20% solids and less than 90% solids, at least 25% solids and less than 90% solids, or at least 30% solids and less than 90% solids. Process water (i.e., water used for processing CO₂ to produce precipitation material comprising carbonates, bicarbonates, or a mixture of carbonates and bicarbonates) may be partially removed such that the remainder of water in a slurry comprising precipitation material may be used as mix water (e.g., admixture solution) for preparing compositions (e.g., compositions having components such as those described in Table A1 and A2) for producing formed building materials. As such, a slurry comprising precipitation material may be dewatered such that the water:precipitation material is less than 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, or 0.1 (measured as one would measure water:cement in preparing a cement or concrete mixture). A slurry comprising precipitation material may be dewatered such that the water:precipitation material is more than 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, or 0.7 (measured as one would measure water:cement in preparing a cement or concrete mixture). Combinations of the foregoing are also useful. For example, in some embodiments, a slurry comprising precipitation material may be dewatered such that the water:precipitation material is less than 0.6 and more than 0.1, less than 0.5 and more than 0.2, or less than 0.4 and more than 0.2.

The resultant dewatered precipitation material (e.g., composition comprising carbonates, bicarbonates, or combinations thereof), which may still carry residual water, may then be dried, as desired, to produce a dry precipitation material. Optionally, the dewatered precipitation material may be washed before drying. For example, the precipitation material may be washed with freshwater to remove salts (such as NaCl) from the dewatered precipitation material before drying. Drying may be achieved by air drying the dewatered precipitation material. Where the dewatered precipitation material is air dried, air drying may be at room or elevated temperature. Elevated temperatures, in some embodiments, are greater than room temperature, such as greater than 20° C., 30° C., 40° C., 50° C., 60° C., 70° C., 80° C., 90° C., 100° C., 110° C., 120° C., 130° C., 140° C., 150° C., 160° C., 170° C., 180° C., 190° C., 200° C., 210° C., 220° C., 230° C., 240° C., or 250° C. Elevated temperatures, in some embodiments, are less than 250° C., 240° C., 230° C., 220° C., 210° C., 200° C., 190° C., 180° C., 170° C., 160° C., 150° C., 140° C., 130° C., 120° C., 110° C., 100° C., 90° C., 80° C., 70° C., 60° C., 50° C., 40° C., 30° C., or 20° C., but greater than room temperature. Combinations of the foregoing may be useful in describing the elevated temperatures that may be used to dry precipitation material. For example, in some embodiments, precipitation material may be dried at greater than 25° C. and less than 100° C., greater than 35° C. and less than 90° C., greater than 35° C. and less than 90° C., greater than 50° C. and less than 90° C., and greater than 60° C. and less than 85° C. Elevated temperatures may be attained in any conventional manner or apparatus commonly used for drying. In some embodiments, for example, a conventional apparatus that may be used for drying precipitation material is an oven. In some embodiments, dewatered precipitation material may be spray dried to dry the precipitation material, wherein a slurry comprising the precipitation material (optionally in process water or fresh water, for example, after washing to remove soluble salts) may be dried by feeding it through a hot gas (such as the gaseous waste stream from the power plant) (e.g., the slurry feed may be pumped through an atomizer into a main drying chamber and a hot gas may be passed as a co-current or counter-current to the atomizer direction. In some embodiments, dewatered precipitation material is dried using a swirl fluidizer. Depending on the particular drying protocol, the system may comprise a drying station that includes a filtration element, freeze drying structure, spray drying structure, etc. Precipitation material that has been dried (e.g., spray dried; dried by swirl fluidizer) may be more than 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 99.9% solids. Precipitation material that has been dried (e.g., spray dried; dried by swirl fluidizer) may be less than 99.9%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, or 80% (w/w) or (w/v) solids. Combinations of the foregoing may also be useful for describing precipitation material that has been dried. For example, in some embodiments, precipitation material that has been dried may be more than 80% and less than 99.9% solids, more than 85% and less than 99.9% solids, or more than 95% and less than 99.9% solids.

In certain embodiments, the precipitation material may be refined (i.e., processed), though it need not necessarily be refined, in some manner prior to subsequent use as a sequestered-CO₂ component. Refinement may include a variety of different protocols and may be performed on precipitation material comprising residual water, or precipitation material that has been further dried. In certain embodiments, the product may be subjected to mechanical refinement in order to obtain a product with desired physical properties (e.g., particle size, etc.). Grinding the precipitation material may be effected by any conventional grinder, including, but not limited to a ball mill, a rod mill, an autogenous mill, a semi-autogenous grinding (“SAG”) mill, a pebble mill, a high pressure grinding roll, a buhrstone mill, a vertical shaft impactor mill (VSI mill), a tower mill, and a vibratory mill. The mean particle size of particles in precipitation material described herein may be at least 0.1, 0.05, 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 75, 100, 150, 200, 250, 300, 350, 400, 450, 500, 600, 700, 800, 900, or 1000 microns, before or after refinement. In some embodiments, the mean particle size of particles in precipitation material described herein may be less than 1000, 900, 800, 700, 600, 500, 450, 400, 350, 300, 250, 200, 150, 100, 75, 50, 45, 40, 35, 30, 25, 20, 15, 10, 5, 1, 0.5, or 0.1 microns, before or after refinement. Combinations of the foregoing ranges (e.g., at 20 least 0.1 microns and less than 100 microns; at least 1 micron and less than 100 microns; at least 1 micron and less than 50 microns; at least 10 microns and less than 40 microns; etc.) may also be used to describe the mean particle size of precipitation material.

FIG. 1 provides a schematic flow diagram of a process for producing precipitation material comprising carbonates, bicarbonates, or a combination thereof. In FIG. 1, saltwater from saltwater source 110 is subjected to precipitation conditions (e.g., carbonate compound precipitation conditions) at precipitation step 120. As reviewed above, saltwater refers to any of a number of different types of aqueous fluids other than freshwater, including brackish water, seawater and brine (including man-made brines, e.g., geothermal plant wastewaters, desalination waste waters, etc), as well as other salines having a salinity that is greater than that of freshwater. The saltwater source from which the carbonate compound composition of the cements is derived may be a naturally occurring source, such as a sea, ocean, lake, swamp, estuary, lagoon, etc., or a man-made source.

In certain embodiments, the water may be obtained from the power plant that is also providing the gaseous waste stream. For example, in water cooled power plants, such as seawater cooled power plants, water that has been employed by the power plant may then be sent to the precipitation system and employed as the water in the precipitation reaction. In certain of these embodiments, the water may be cooled prior to entering the precipitation reactor.

In the embodiment depicted in FIG. 1, the water from saltwater source 110 is first charged with CO₂ to produce CO₂ charged water, which CO₂ is then subjected to carbonate compound precipitation conditions. As depicted in FIG. 1, a CO₂ gaseous stream 130 is contacted with the water at precipitation step 120. The provided gaseous stream 130 is contacted with a suitable water at precipitation step 120 to produce a CO₂ charged water. By CO₂ charged water is meant water that has had CO₂ gas contacted with it, where CO₂ molecules have combined with water molecules to produce, e.g., carbonic acid, bicarbonate and carbonate ion. Charging water in this step results in an increase in the CO₂ content of the water, e.g., in the form of carbonic acid, bicarbonate and carbonate ion, and a concomitant decrease in the pCO₂ of the waste stream that is contacted with the water. The CO₂ charged water is acidic, having a pH of 6 or less, such as 5 or less and including 4 or less. In certain embodiments, the concentration of CO₂ of the gas that is used to charge the water is 10% or higher, 25% or higher, including 50% or higher, such as 75% or even higher. Contact protocols of interest include, but are not limited to: direct contacting protocols, e.g., bubbling the gas through the volume of water, concurrent contacting means, i.e., contact between unidirectionally flowing gaseous and liquid phase streams, countercurrent means, i.e., contact between oppositely flowing gaseous and liquid phase streams, and the like. Thus, contact may be accomplished through use of infusers, bubblers, fluidic Venturi reactor, sparger, gas filter, spray, tray, or packed column reactors, and the like, as may be convenient.

At precipitation step 120, carbonate compounds, which may be amorphous or crystalline, are precipitated. Precipitation conditions of interest include those that change the physical environment of the water to produce the desired precipitation material. For example, the temperature of the water may be raised to an amount suitable for precipitation of the desired carbonate compound(s) to occur. In such embodiments, the temperature of the water may be raised to a value from 5 to 70° C., such as from 20 to 50° C. and including from 25 to 45° C. As such, while a given set of precipitation conditions may have a temperature ranging from 0 to 100° C., the temperature may be raised in certain embodiments to produce the desired precipitation material. In certain embodiments, the temperature is raised using energy generated from low or zero carbon dioxide emission sources, e.g., solar energy source, wind energy source, hydroelectric energy source, etc. While the pH of the water may range from 7 to 14 during a given precipitation process, in certain embodiments the pH is raised to alkaline levels in order to drive the precipitation of carbonate compound as desired. In certain of these embodiments, the pH is raised to a level that minimizes if not eliminates CO₂ gas generation production during precipitation. In these embodiments, the pH may be raised to 10 or higher, such as 11 or higher. Where desired, the pH of the water is raised using any convenient approach. In certain embodiments, a pH-raising agent may be employed, where examples of such agents include oxides, hydroxides (e.g., sodium hydroxide, potassium hydroxide, brucite), carbonates (e.g. sodium carbonate) and the like. The amount of pH-elevating agent that is added to the saltwater source will depend on the particular nature of the agent and the volume of saltwater being modified, and will be sufficient to raise the pH of the saltwater source to the desired value. Alternatively, the pH of the saltwater source can be raised to the desired level by electrolysis of the water.

CO₂ charging and carbonate compound precipitation may occur in a continuous process or at separate steps. As such, in some embodiments, charging and precipitation may occur in the same reactor of a system (e.g., as illustrated in FIG. 1 at step 120). In yet other embodiments, these two steps may occur in separate reactors, such that the water is first charged with CO₂ in a charging reactor and the resultant CO₂ charged water is then subjected to precipitation conditions in a separate reactor.

Following production of precipitation material (e.g., material comprising carbonates, bicarbonates, or a combination thereof) from the water, the precipitation material may be separated from some or all the mother liquor to produce separated precipitation material, as illustrated at step 140 of FIG. 1. Separation of the precipitation material may be achieved using any convenient approach, including a mechanical approach, e.g., where bulk excess water is drained from the precipitation material, e.g., either by gravity alone or with the addition of vacuum, mechanical pressing, by filtering the precipitation material from the mother liquor to produce a filtrate, etc. For exemplary system and methods for bulk water removal that may be used, see U.S. Provisional Patent Application Nos. 61/158,992, filed 10 Mar. 2009; 61/168,166, filed 9 Apr. 2009; 61/170,086, filed 16 Apr. 2009; 61/178,475, filed 14 May 2009; 61/228,210, filed 24 Jul. 2009; 61/230,042, filed 30 Jul. 2009; and 61/239,429, filed 2 Sep. 2009, each of which is incorporated herein by reference. Separation of bulk water produces a wet or dewatered precipitation material.

Dewatered precipitation material may be used directly in formed building materials described herein, or the dewatered precipitation material may be further dried. In some embodiments, the dewatered precipitation material may be used directly. Directly using the resultant dewatered precipitation material is convenient in applications that require some amount of water. In a non-limiting example, dewatered precipitation material may be mixed with ordinary Portland cement, wherein the dewatered precipitation material provides at least a portion of the water needed for hydration and placement of the cement mixture. In some embodiments, the dewatered precipitation material is more than 5% water, more than 10% water, more than 20% water, more than 30% water, more than 50% water, more than 60% water, more than 70% water, more than 80% water, more than 90% water, or more than 95% water. In some embodiments, the dewatered precipitation material provides at least 5% of the water, at least 10% of the water, at least 20% of the water, at least 30% of the water, at least 40% of the water, at least 50% of the water, at least 60% of the water, at least 70% of the water, at least 80% of the water, at least 90% of the water, or at least 95% of the water needed for the application that the dewatered precipitation material is being used. In some embodiments, the dewatered precipitation material provides all of the water needed for the application that the dewatered precipitation material is being used. For example, the dewatered precipitation material may provide all of the water needed for hydration and placement of a cement mixture of dewatered precipitation material and ordinary Portland cement. For instance, precipitation material may be dewatered such that the dewatered precipitation material comprises nearly 70% water, such as 66.5% water. The slurry of precipitation material may then be mixed with ordinary Portland cement such that the resultant cement mixture comprises 80% ordinary Portland cement and 20% precipitation material, wherein the water to cement (i.e., ordinary Portland cement and precipitation material) ratio is about 40%. By controlling the amount of water that is removed from the precipitation material, the carbon footprint of the material (e.g., concrete, formed building materials, etc.) being made from the precipitation material is being controlled as well, especially if the material requires water. With this in mind, the low, neutral, or negative carbon footprint of any of the product materials described herein may be further reduced by removing only as much water as needed from the precipitation material.

As described above, the resultant dewatered precipitation material may also be dried to produce a product, as illustrated at step 160 of FIG. 1. Drying may be achieved by air-drying the filtrate. Where the filtrate is air dried, air-drying may be at room or elevated temperature. Dewatered precipitation material may be air dried to produce a precipitation material that is less than 50% water, less than 40% water, less than 30% water, less than 20% water, less than 10% water, or less than 5% water. For example, dewatered precipitation material may be air dried to produce a precipitin material that is 30% or less water. Such precipitation material may be crushed with or without additional processing (e.g., high sheer mixing) and combined with other materials such as ordinary Portland cement to produce a cement mixture comprising a portion of the water needed for hydration and placement of the cement mixture. Drying may also be achieved by spray drying the precipitation material, where the liquid containing the precipitation material is dried by feeding it through a hot gas (such as the gaseous waste stream from the power plant), e.g., where the liquid feed is pumped through an atomizer into a main drying chamber and a hot gas is passed as a co-current or counter-current to the atomizer direction. Depending on the particular drying protocol of the system, the drying station may include a filtration element, freeze drying structure, spray drying structure, etc.

Where desired, the dewatered precipitation material from the separation reactor 140 may be washed before drying, as illustrated at optional step 150 of FIG. 1. The precipitation material may be washed with freshwater, e.g., to remove salts (such as NaCl) from the dewatered precipitation material. Used wash water may be disposed of as convenient, e.g., by disposing of it in a tailings pond, etc.

At step 170, the dried precipitation material is optionally refined, for example, to provide for desired physical characteristics, such as particle size, surface area, etc., or to add one or more components to the precipitation material, such as admixtures, aggregate, supplementary cementitious materials, etc., to produce a final product 180. With respect to particle size, and optionally after refining, the mean particle size of particles in the precipitation material, which may comprise vaterite, calcite, aragonite, amorphous calcium carbonate, or any combination thereof, may be at least 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 75, 100, 150, 200, 250, 300, 350, 400, 450, 500, 600, 700, 800, 900, or 1000 microns. In some embodiments, optionally after refining, the mean particle size of particles in the precipitation material, which may comprise vaterite, calcite, aragonite, amorphous calcium carbonate, or any combination thereof, is less than 1000, 900, 800, 700, 600, 500, 450, 400, 350, 300, 250, 200, 150, 100, 75, 50, 45, 40, 35, 30, 25, 20, 15, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.5, or 0.1 microns. Combinations of the foregoing ranges (e.g., at 20 least 0.1 microns and less than 100 microns; at least 1 micron and less than 100 microns; at least 1 micron and less than 50 microns; at least 10 microns and less than 40 microns; etc.) may also be used to describe the mean particle size of precipitation material. In certain embodiments, precipitation material may be made up of particles having an average particle size ranging from 0.1 to 100 microns, such as 10 to 40 microns as determined using any convenient particle size determination protocol, such as multi-detector laser scattering or sieving (i.e. <38 microns). In certain embodiments, multimodal, (e.g., bimodal or other) distributions are present. Bimodal distributions allow the surface area to be minimized, thus allowing a lower liquids/solids mass ratio for the cement yet providing smaller reactive particles for early reaction. In these instances, the average particle size of the larger size class can be upwards of 1000 microns (1 mm) The surface area of the components making up the precipitation material may vary. A given cement may have an average surface area sufficient to provide for a liquids to solids ratio upon combination with a liquid to produce a formed building material ranging from 0.5 m²/gm to 50 m²/gm, such as 0.75 to 20 m²/gm and including 0.80 to 10 m²/gm. In certain embodiments, the surface area of the cement ranges from 0.9 to 5 m²/gm, such as 0.95 to 2 m²/gm and including 1 to 2 m²/gm, as determined using the surface area determination protocol described in Breunner, Emmit, and Teller (1953).

The precipitation material, and, hence, the sequestered-CO₂ component, may comprise metastable carbonate compounds precipitated from a solution of divalent cations, such as a saltwater, as described herein; however, the carbonate compounds are not limited to metastable carbonate compounds. Carbonate compounds may include precipitated crystalline and/or amorphous carbonate compounds. Specific carbonate minerals of interest include, but in no way are limited to, calcium carbonate minerals, magnesium carbonate minerals, and calcium magnesium carbonate minerals. Calcium carbonate minerals of interest include, but are not limited to, calcite (CaCO₃), aragonite (CaCO₃), vaterite (CaCO₃), ikaite (CaCO₃.6H₂O), and amorphous calcium carbonate (CaCO₃.nH₂O). In some embodiments, the precipitation material, and, hence, the sequestered-CO₂ component, may comprise at least 1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 96, 97, 98, 99, 99.9% amorphous calcium carbonate, with the remaining precipitation material comprising calcite, aragonite, vaterite, or some combination thereof. In some embodiments, the precipitation material, and, hence, the sequestered-CO₂ component, may comprise less than 99.9, 99, 98, 97, 96, 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, 5, 4, 3, 2, or 1% amorphous calcium carbonate, with the remaining precipitation material comprising calcite, aragonite, vaterite, or some combination thereof. For example, in some embodiments the precipitation material comprises at least 1% and less than 25% amorphous calcium carbonate, at least 1% and less than 20% amorphous calcium carbonate, at least 1% and less than 15% amorphous calcium carbonate, or at least 1% and less than 10% amorphous calcium carbonate. In some embodiments, the sequestered-CO₂ component of the building materials may comprise at least 1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 96, 97, 98, 99, 99.9% vaterite, with the remaining precipitation material comprising calcite, aragonite, amorphous calcium carbonate, or some combination thereof. In some embodiments, the precipitation material, and, hence, the sequestered-CO₂ component, may comprise less than 99.9, 99, 98, 97, 96, 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, 5, 4, 3, 2, or 1% vaterite, with the remaining precipitation material comprising calcite, aragonite, amorphous calcium carbonate, or some combination thereof. In some embodiments, the precipitation material, and, hence, the sequestered-CO₂ component, may comprise at least 1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 96, 97, 98, 99, 99.9% aragonite, with the remaining precipitation material comprising calcite, vaterite, amorphous calcium carbonate, or some combination thereof. In some embodiments, the precipitation material, and, hence, the sequestered-CO₂ component, may comprise less than 99.9, 99, 98, 97, 96, 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, 5, 4, 3, 2, or 1% aragonite, with the remaining precipitation material comprising calcite, vaterite, amorphous calcium carbonate, or some combination thereof. In some embodiments, the precipitation material, and, hence, the sequestered-CO₂ component, may comprise at least 1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 96, 97, 98, 99, 99.9% calcite, with the remaining precipitation material comprising vaterite, aragonite, amorphous calcium carbonate, or some combination thereof. In some embodiments, the precipitation material, and, hence, the sequestered-CO₂ component, may comprise less than 99.9, 99, 98, 97, 96, 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, 5, 4, 3, 2, or 1% calcite, with the remaining precipitation material comprising vaterite, aragonite, amorphous calcium carbonate, or some combination thereof. In some embodiments, the vaterite to calcite ratio (v/c ratio) is greater than 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, or 99.9 in the precipitation material, and, hence, the sequestered-CO₂ component. In some embodiments, the vaterite to calcite ratio (v/c ratio) is less than 99.9, 90, 80, 70, 60, 50, 40, 30, 20, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 in the precipitation material, and, hence, the sequestered-CO₂ component. Some precipitation material may be better described in terms of the calcite to vaterite ratio (c/v ratio), especially when there is a greater amount of calcite in the precipitation material than vaterite. In some embodiments, for example, the calcite to vaterite ratio (c/v ratio) is greater than 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, or 99.9 in the precipitation material, and, hence, the sequestered-CO₂ component. In some embodiments, the calcite to vaterite ratio (c/v ratio) is less than 99.1, 90, 80, 70, 60, 50, 20 40, 30, 20, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 in the precipitation material, and, hence, the sequestered-CO₂ component. As indicated herein, the carbonate compounds of precipitation material may be metastable carbonate compounds (and may include one or more metastable hydroxide compounds) that are more stable in saltwater than in freshwater, such that upon contact with fresh water of any pH they (e.g., metastable carbonates such as amorphous calcium carbonate; vaterite; etc.) dissolve and re-precipitate into other fresh water stable compounds (e.g., minerals such as low-Mg calcite). Such a thermodynamic driving force may be exploited in the manufacture of derived materials (e.g., formed building materials). For example, in some embodiments, metastable carbonate compounds may be stored in a stabilizing amount of the saltwater (optionally containing additional metastable carbonate compound stabilizers) from which the metastable carbonate compounds were precipitated, and washed with fresh water prior to or during use to facilitate the transformation of metastable carbonate compounds to more stable carbonate compounds (e.g., amorphous calcium carbonate to vaterite; vaterite to aragonite; vaterite to calcite; etc.). Such a transformation may be exploited for its self-cementing properties. For example, a sample of precipitation material comprising 95% vaterite and 5% aragonite with an initial compressive strength of 0 psi may comprise 19% vaterite and 81% aragonite with a compressive strength of 2260 psi at 14 days, and may comprise 0% vaterite and 100% aragonite with a compressive strength of 3300 psi at 28 days. SEM images and XRD diffractograms of the foregoing sample of precipitation material may be found in FIG. 10. This self-cementing property of metastable compounds may be used to make formed building materials as described herein. With respect to magnesium carbonate minerals, precipitation material, and, hence, the CO₂-sequestering component, may include, but is not limited to magnesite (MgCO₃), barringtonite (MgCO₃.2H₂O), nesquehonite (MgCO₃.3H₂O), lanfordite (MgCO₃.5H₂O), and amorphous magnesium calcium carbonate (MgCO₃.nH₂O). Calcium magnesium carbonate minerals of interest include, but are not limited to dolomite (CaMgCO₃), huntite (CaMg₃(CO₃)₄), and sergeevite (Ca₂Mg₁₁(CO₃)₁₃.H₂O). In certain embodiments, non-carbonate compounds like brucite (Mg(OH)₂) may also form in combination with the compounds listed above. As indicated above, the compounds of the carbonate compound compositions may be metastable carbonate compounds (and may include one or more metastable hydroxide compounds) that are more stable in saltwater than in freshwater, such that upon contact with fresh water of any pH they dissolve and re-precipitate into other fresh water stable compounds, e.g., minerals such as low-Mg calcite. Such a phenomenon may be exploited in the manufacture of formed building materials. For example, in some embodiments, metastable carbonate compounds may be stored in a stabilizing amount of the saltwater (optionally containing additional metastable carbonate compound stabilizers) from which the metastable carbonate compounds were precipitated, and washed with fresh water prior to or during use to facilitate the transformation of metastable carbonate compounds to more stable carbonate compounds.

As the precipitation material (e.g., carbonates, bicarbonates, or the combination thereof) may be derived from (e.g., precipitated from) water, the precipitation material, and, hence, the sequestered-CO₂ component, may include one or more components that are present in the water from which they are derived. For example, where the solution of divalent cations is saltwater, the precipitation material may include one or more constituents (“markers”) found in the saltwater source. For example, if the saltwater source is seawater, seawater constituents that may be present in precipitation material include, but are not limited to chloride, sodium, sulfur, potassium, bromide, silicon, strontium, and the like. Any such markers are generally present in small amounts, such as 20,000 ppm or less or 2000 ppm or less. In some embodiments, and without being limited to seawater, the marker in the precipitation material may be strontium, ranging from 10,000 ppm or less, 3 to 10,000 ppm or less, 5 to 5000 ppm or less, 5 to 1000 ppm or less, 5 to 500 ppm or less, or 5 to 100 ppm or less. In embodiments in which the precipitation material comprises aragonite, the strontium may be incorporated in the aragonite lattice. Markers present in the compositions may vary depending upon the particular water source employed to produce the precipitation material. Also of interest are isotopic markers that identify the water source.

Sequestered-CO₂ components (e.g., components comprising precipitation material comprising carbonates, bicarbonates, or a combination thereof) comprise CO₂ that otherwise would have been released into the atmosphere, most of which results from burning fossil fuels, which fuels are originally of plant origin. As such, sequestered-CO₂ components, which components comprise one or more synthetic carbonates derived from industrial CO₂, reflect the relative carbon isotope composition (δ¹³C) of the fossil fuel (e.g., coal, oil, natural gas, or flue gas) from which the industrial CO₂ (from combustion of the fossil fuel) was derived. The relative carbon isotope composition (δ¹³C) value with units of % (per mille) is a measure of the ratio of the concentration of two stable isotopes of carbon, namely ¹²C and ¹³C, relative to a standard of fossilized belemnite (the PDB standard).

δ¹³C %=[(¹³C/¹²C_(sample)−¹³C/¹²C_(PDB standard))/(¹³C/¹²C_(PDB standard))]×1000

As such, the δ¹³C value of the carbon in precipitation material (e.g., synthetic carbonates, bicarbonates, or a combination thereof) described herein serves as a fingerprint for a CO₂ gas source, especially CO₂ released from burning fossil fuel. The δ¹³C value may vary from source to source (i.e., fossil fuel source), but the δ¹³C value for sequestered-CO₂ components generally, but not necessarily, ranges between −9% to −35%. In some embodiments, the δ¹³C value of the carbon in the precipitation material is between −1% and −50%, between −5% and −40%, between −5% and −35%, between −7% and −40%, between −7% and −35%, between −9% and −40%, or between −9% and −35%. In some embodiments, the δ¹³C value of the carbon in the precipitation material is less than (i.e., more negative than) 0, −1%, −2%, −3%, −5%, −6%, −7%, −8%, −9%, −10%, −11%, −12%, −13%, −14%, −15%, −16%, −17%, −18%, −19%, −20%, −21%, −22%, −23%, −24%, −25%, −26%, −27%, −28%, −29%, −30%, −31%, −32%, −33%, −34%, −35%, −36%, −37%, −38%, −39%, −40%, −41%, −42%, −43%, −44%, −45%, −46%, −47%, −48%, −49%, or −50, wherein the more negative the δ¹³C value, the more rich the synthetic carbonates, bicarbonates, or a combination thereof is in ¹²C. In some embodiments, the δ¹³C value for carbon-containing compounds or compositions is more than (i.e., less negative than) −50%, −49%, −48%, −47%, −46%, −45%, −44%, −43%, −42%, −41%, −40%, −39%, −38%, −37%, −36%, −35%, −34%, −33%, −32%, −31%, −30%, −29%, −28%, −27%, −26%, −25%, −24%, −23%, −22%, −21%, −20%, −19%, −18%, −17%, −16%, −15%, −14%, −13%, −12%, −11%, −10%, −9%, −8%, −7%, −6%, −5%, −4%, −3%, −2%, −1%, or 0. Combinations of the foregoing ranges are also possible. For example, in some embodiments, the δ¹³C value of the carbon in the precipitation material is less than −1% and more than −50%, less than −5% and more than −50%, less than −10% and more than −50%, less than −15% and more than −50%, or less than −20% and more than −50%. Any suitable method may be used for measuring the δ¹³C value, methods including, but not limited to, mass spectrometry or off-axis integrated-cavity output spectroscopy (off-axis ICOS).

With respect to formed building materials provided herein, such as roadway materials, bricks, blocks, boards (e.g., cement boards), conduits, beams, basins, columns, tiles, fiber-siding products (e.g., fiber-cement siding), slabs, acoustic barriers, drywall, insulation, or combinations thereof containing a sequestered-CO₂ component (e.g., component comprising carbonates, bicarbonates, or combinations thereof), carbon in the sequestered-CO₂ component, and the formed building material itself, particularly if the formed building material comprises a substantial amount of sequestered-CO₂ component (e.g., >50% up to 100% [w/w]), may have a δ¹³C value less than −5%. In some embodiments, the δ¹³C value for the formed building material is between −1% and −50%, between −5% and −40%, between −5% and −35%, between −7% and −40%, between −7% and −35%, between −9% and −40%, or between −9% and −35%. In some embodiments, the δ¹³C value for the formed building material is less than (i.e., more negative than) 0, −1%, −2%, −3%, −5%, −6%, −7%, −8%, −9%, −10%, −11%, −12%, −13%, −14%, −15%, −16%, −17%, −18%, −19%, −20%, −21%, −22%, −23%, −24%, −25%, −26%, −27%, −28%, −29%, −30%, −31%, −32%, −33%, −34%, −35%, −36%, −37%, −38%, −39%, −40%, −41%, −42%, −43%, −44%, −45%, −46%, −47%, −48%, −49%, or −50, wherein the more negative the δ¹³C value, the more rich the carbonate-containing material is in ¹²C. In some embodiments, the δ¹³C value for the formed building material is more than (i.e., less negative than) −50%, −49%, −48%, −47%, −46%, −45%, −44%, −43%, −42%, −41%, −40%, −39%, −38%, −37%, −36%, −35%, −34%, −33%, −32%, −31%, −30%, −29%, −28%, −27%, −26%, −25%, −24%, −23%, −22%, −21%, −20%, −19%, −18%, −17%, −16%, −15%, −14%, −13%, −12%, −11%, −10%, −9%, −8%, −7%, −6%, −5%, −4%, −3%, −2%, −1%, or 0, wherein the less negative the δ¹³C value, the less rich the carbonate-containing material is in ¹²C. Combinations of the foregoing ranges are also possible. In some embodiments, the δ¹³C value for the formed building material is less than −1% and more than −50%, less than −5% and more than −50%, less than −10% and more than −50%, less than −15% and more than −50%, or less than −20% and more than −50%.

In certain embodiments, a system is employed to perform the foregoing methods and compositions.

Following production of the sequestered-CO₂ component, for example, as described above, the sequestered-CO₂ component (e.g., precipitation material; component comprising carbonates, bicarbonates, or a combination thereof) may then be employed to produce a formed building material. Formed building materials may be prepared in accordance with traditional manufacturing protocols for such structures, with the exception that an amount of sequestered-CO₂ component is employed. The portion of conventional components replaced with the sequestered-CO₂ component may vary depending upon the formed building material or application, and in certain instances is 5% by weight or more, including 10% by weight or more, 15% by weight or more, 20% by weight or more, 25% by weight or more, 30% by weight or more, 50% by weight or more, 70% by weight or more, 75% by weight or more, 80% by weight or more, 85% by weight or more, 90% by weight or more, 95% by weight or more, 99% by weight or more, or even 100% by weight. For example, in some embodiments, 20% by weight of more of the conventional cement component (e.g., OPC) may be replaced with sequestered-CO₂ component for producing formed building materials described herein. In some embodiments, 100% by weight of the conventional cement component (e.g., OPC) may be replaced with sequestered-CO₂ component for producing formed building materials described herein.

Table A1 below gives various combinations of components (e.g., cement component, aggregate, supplementary cementitious material (“SCM”)) that may be used in mixtures for production of formed building materials, wherein the sequestered-CO₂ component is used to the exclusion of any additional cement component such as ordinary Portland cement (OPC).

TABLE A1 Compositions for formed building materials Cement component Aggregate Sequestered-CO₂ Fine Coarse SCM Compo- Component (Cement Aggre- Aggre- Fly Meta- sition Substitute) gate gate Ash Slag kaolin 1 X 2 X X 3 X X X 4 X X X X 5 X X X X X 6 X X X X X X 7 X X X X X 8 X X X X X 9 X X X X 10 X X 11 X X X 12 X X X X 13 X X X X X 14 X X X 15 X X X X 16 X X X X X 17 X X X X 18 X X X X 19 X X X 20 X X X 21 X X X X 22 X X X X X 23 X X X X 24 X X X X 25 X X X 26 X X 27 X X X 28 X X X X 29 X X X 30 X X X 31 X X The fine aggregate described in the Table A1 may be conventional fine aggregate such as sand or fine aggregate comprising sequesterd-CO₂ component as described in U.S. patent application Ser. No. 12/475,378, filed 29 May 2009, which application is incorporated herein by reference in its entirety. The coarse aggregate described in the Table A1 may be conventional coarse aggregate such as gravel, crushed stone, slag, recycled concrete, geosynthetic aggregate, glass, or coarse CO₂-sequestering aggregate as described in U.S. patent application Ser. No. 12/475,378. Fly ash, slag, and/or metakaolin are considered supplementary cementitious materials to a skilled person the art.

Surprisingly, it was discovered that the sequestered-CO₂ component, to the exclusion of any additional cement component(s), acts much like a conventional cement (e.g., OPC). The sequestered-CO₂ component, when prepared (e.g., mix water added, cast as a formed building material, etc.) and allowed to harden, achieved high compressive strengths as described below in reference to the compressive strengths of formed building materials comprised of the compositions of Table A1. Compositions comprising fine aggregate such as sand, which may be prepared (e.g., mixed, mix water added, cast as a formed building material, etc.) and allowed to harden, achieved high compressive strengths as described below in reference to the compressive strengths of formed building materials comprised of the compositions of Table A1. Such compositions comprising sequestered-CO₂ component behave much like conventional cement, binding the fine aggregate (e.g., sand) as shown in FIG. 11. Binary mixtures of sequestered-CO₂ component and fine aggregate (e.g., sand), may comprise at least 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, or 95% by weight fine aggregate (e.g., sand), the remainder being sequestered-CO₂ component as described herein. Binary mixtures of sequestered-CO₂ component and fine aggregate (e.g., sand), may comprise less than 95%, 94%, 93%, 92%, 91%, 90%, 89%, 88%, 87%, 86%, 85%, 84%, 83%, 82%, 81%, 80%, 79%, 78%, 77%, 76%, 75%, 74%, 73%, 72%, 71%, 70%, 69%, 68%, 67%, 66%, 65%, 64%, 63%, 62%, 61%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, or 1% by weight fine aggregate (e.g., sand), the remainder being sequestered-CO₂ component as described herein. Combinations of the foregoing are also useful for describing binary mixtures comprising sequestered-CO₂ component and fine aggregate (e.g., sand). For example, in some embodiments, such binary mixtures of sequestered-CO₂ component and fine aggregate (e.g., sand), may comprise at least 1% and less than 95% fine aggregate by weight, at least 25% and less than 95% fine aggregate by weight, at least 50% and less than 95% fine aggregate by weight, at least 50% and less than 90% fine aggregate by weight, at least 50% and less than 85% fine aggregate by weight, at least 55% and less than 85% fine aggregate by weight. In some embodiments, such binary mixtures of sequestered-CO₂ component and fine aggregate (e.g., sand) comprise at least 65% and less than 95% fine aggregate (e.g., sand) by weight, with a compressive strength of at least 3000 psi and less than 8000 psi, and optionally with a porosity of at least 25% and less than 60%. In some embodiments, such binary mixtures of sequestered-CO₂ component and fine aggregate (e.g., sand) comprise at least 85% and less than 95% fine aggregate (e.g., sand) by weight, with a compressive strength of at least 3000 psi and less than 8000 psi, and optionally with a porosity of at least 25% and less than 60%. In some embodiments, such binary mixtures of sequestered-CO₂ component and fine aggregate (e.g., sand) comprise at least 75% and less than 85% fine aggregate (e.g., sand) by weight, with a compressive strength of at least 3000 psi and less than 8000 psi, and optionally with a porosity of at least 25% and less than 60%. In some embodiments, such binary mixtures of sequestered-CO₂ component and fine aggregate (e.g., sand) comprise at least 70% and less than 80% fine aggregate (e.g., sand) by weight, with a compressive strength of at least 3000 psi and less than 8000 psi, and optionally with a porosity of at least 25% and less than 60%. In some embodiments, such binary mixtures of sequestered-CO₂ component and fine aggregate (e.g., sand) comprise at least 65% and less than 75% fine aggregate (e.g., sand) by weight, with a compressive strength of at least 3000 psi and less than 8000 psi, and optionally with a porosity of at least 25% and less than 60%. The foregoing compositions may further comprise one more admixtures or additives (e.g., GLENIUM® 7500). It should also be noted that drying formed building materials comprising cement substitute (e.g., sequestered-CO₂ component to the exclusion of any additional cementitious components) has been found to have a surprising effect on compressive strength and porosity of such compositions.

Coarse aggregate may be used in place of some or all of the fine aggregate in the foregoing binary compositions of sequestered-CO₂ and fine aggregate to produce formed building materials. As such, the foregoing binary compositions of sequestered-CO₂ and fine aggregate may comprise at least 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.9%, or 100% by weight coarse aggregate (e.g., rock), wherein the amount of coarse aggregate by weight replaces an equivalent amount by weight of fine aggregate (e.g., sand), and wherein the remainder of the composition comprises sequestered-CO₂ as described herein. The foregoing binary compositions of sequestered-CO₂ and fine aggregate may comprise less than 100%, 99.9%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 89%, 88%, 87%, 86%, 85%, 84%, 83%, 82%, 81%, 80%, 79%, 78%, 77%, 76%, 75%, 74%, 73%, 72%, 71%, 70%, 69%, 68%, 67%, 66%, 65%, 64%, 63%, 62%, 61%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, or 1% by weight coarse aggregate (e.g., rock), wherein the amount of coarse aggregate by weight replaces an equivalent amount by weight of fine aggregate (e.g., sand), and wherein the remainder of the composition comprises sequestered-CO₂ component as described herein. Combinations of the foregoing are also useful for describing compositions comprising sequestered-CO₂ component, fine aggregate, and/or coarse aggregate. For example, in some embodiments, the compositions, which may be considered ternary mixtures of sequestered-CO₂ component, fine aggregate (e.g., sand), and coarse aggregate (e.g., rock) may comprise at least 1% and less than 95% coarse aggregate by weight, at least 25% and less than 95% coarse aggregate by weight, at least 50% and less than 95% coarse aggregate by weight, at least 50% and less than 90% coarse aggregate by weight, at least 50% and less than 85% coarse aggregate by weight, at least 55% and less than 85% coarse aggregate by weight, wherein the amount of coarse aggregate by weight replaces an equivalent amount by weight of fine aggregate (e.g., sand), and wherein the remainder of the composition comprises sequestered-CO₂ component as described herein. In some embodiments, a composition comprises at least 65% and less than 95% aggregate (e.g., mixture of fine aggregate such as sand and coarse aggregate such as rock) by weight, with a compressive strength of at least 3000 psi and less than 8000 psi, and optionally with a porosity of at least 25% and less than 60%. In some embodiments, a composition comprises at least 85% and less than 95% aggregate (e.g., mixture of fine aggregate such as sand and coarse aggregate such as rock) by weight, with a compressive strength of at least 3000 psi and less than 8000 psi, and optionally with a porosity of at least 25% and less than 60%. In some embodiments, a composition comprises at least 75% and less than 85% aggregate (e.g., mixture of fine aggregate such as sand and coarse aggregate such as rock) by weight, with a compressive strength of at least 3000 psi and less than 8000 psi, and optionally with a porosity of at least 25% and less than 60%. In some embodiments, a composition comprises at least 70% and less than 80% aggregate (e.g., mixture of fine aggregate such as sand and coarse aggregate such as rock) by weight, with a compressive strength of at least 3000 psi and less than 8000 psi, and optionally with a porosity of at least 25% and less than 60%. In some embodiments, a composition comprises at least 65% and less than 75% aggregate (e.g., mixture of fine aggregate such as sand and coarse aggregate such as rock) by weight, with a compressive strength of at least 3000 psi and less than 8000 psi, and optionally with a porosity of at least 25% and less than 60%. The foregoing compositions may further comprise one more admixtures or additives (e.g., GLENIUM® 7500), which may provide improved performance for formed building materials as described herein. It should also be noted that drying formed building materials comprising cement substitute has been found to have a surprising effect on compressive strength and porosity of such compositions comprising cement substitute.

Porosity of formed building materials produced from the compositions of Table A1, in which the cement component is sequestered-CO₂ component described herein to the exclusion of any additional cement components (e.g., OPC), may be, in some embodiments, at least 5%, 10%, 15%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 75%, 80%, 85%, 90%, or 95%. In some embodiments, the porosity of formed building materials produced from the compositions of Table A1 may be less than 95%, 90%, 85%, 80%, 75%, 70%, 69%, 68%, 67%, 66%, 65%, 64%, 63%, 62%, 61%, 60%, 59%, 58%, 57%, 56%, 55%, 54%, 53%, 52%, 51%, 50%, 49%, 48%, 47%, 46%, 45%, 44%, 43%, 42%, 41%, 40%, 39%, 38%, 37%, 36%, 35%, 34%, 33%, 32%, 31%, 30%, 29%, 28%, 27%, 26%, 25%, 24%, 23%, 22%, 21%, 20%, 15%, 10%, or 5%. Combinations of the foregoing porosities are also useful for describing the porosity of formed building materials produced from the compositions of Table A1. For example, the porosity of a formed building material may be, in some embodiments, at least 20% and less than 70%, such as at least 30% and less than 60%. FIG. 11 provides SEM images of a hardened paste comprising precipitation material that may be used as a complete cement substitute in formed building materials described herein. As shown, such a hardened paste comprises pores that may be occupied by mix water or admixture solution. Formed building materials comprising fine and coarse aggregate may also comprise pores that may be occupied by mix water or admixture solution.

Compressive strengths of formed building materials produced from the compositions of Table A1, in which the cement component is sequestered-CO₂ component described herein to the exclusion of any additional cement components (e.g., OPC), may be, in some embodiments, at least 500 psi, 750 psi, 1000 psi, 1250 psi, 1500 psi, 1750 psi, 2000 psi, 2250 psi, 2500 psi, 2750 psi, 3000 psi, 3250 psi, 3500 psi, 3750 psi, 4000 psi, 4250 psi, 4500 psi, 4750 psi, 5000 psi, 5250 psi, 5500 psi, 5750 psi, 6000 psi, 6250 psi, 6500 psi, 6750 psi, 7000 psi, 7250 psi, 7500 psi, 7750 psi, 8000 psi, 8250 psi, 8500 psi, 8750 psi, 9000 psi, 9,250 psi, 9,500 psi, 9,750 psi, or 10,000 psi at in 1, 7, 14, or 28 days. Compressive strengths of formed building materials produced from the compositions of Table A1, in which the cement component is sequestered-CO₂ component described herein to the exclusion of any additional cement components (e.g., OPC), may be, in some embodiments, less than 10,000 psi, 9750 psi, 9500 psi, 9250 psi, 9000 psi, 8750 psi, 8500 psi, 8250 psi, 8000 psi, 7750 psi, 7500 psi, 7250 psi, 7000 psi, 6750 psi, 6500 psi, 6250 psi, 6000 psi, 5750 psi, 5500 psi, 5250 psi, 5000 psi, 4750 psi, 45000 psi, 4250 psi, 4000 psi, 3750 psi, 3500 psi, 3250 psi, 3000 psi, 2750 psi, 2500 psi, 2250 psi, 2000 psi, 1750 psi, 1500 psi, 1250 psi, 1000 psi, 750 psi, or 500 psi at 1, 7, 14, or 28 days. Combinations of the foregoing compressive strengths are also useful for describing formed building materials produced from the compositions of Table A1, in which the cement component is sequestered-CO₂ component described herein to the exclusion of any additional cement components (e.g., OPC). For example, compressive strengths of formed building materials produced from the compositions of Table A1 in which the cement component is sequestered-CO₂ component described herein to the exclusion of any additional cement components (e.g., OPC) may be, in some embodiments, at least 2000 psi and less than 6000 psi at 1, 7, 14, or 28 days.

Experiments have shown that drying has a surprising effect on the compressive strength of formed building materials comprising the sequestered-CO₂ component described herein. For example, mortar cube were prepared in which 70% of the sequestered-CO₂ component (e.g., precipitation material comprising vaterite as described herein) was replaced with fine aggregate (e.g., sand) according at an ASTM method (C109). Compressive strength after seven days was 4500 psi, and detailed imaging showed that carbonates (either vaterite or another calcium carbonate polymorph such as a lower energy polymorph [e.g., calcite]) of the sequestered-CO₂ component act as a binder of the sand (i.e., the sequestered-CO₂ component acted much like a conventional hydraulic cement such as OPC) (see FIG. 12 for sequestered-CO₂ component binding to sand). Surprisingly, the compressive strength of 4500 psi was achieved for the exemplary mortars in which the residual water was removed by drying at 80° C. Without the removal of the residual water, a compressive strength of 3000 psi was achieved. In some embodiments, the compressive strength of formed building materials comprising sequestered-CO₂ component with aggregate (e.g., fine aggregate such as sand and/or coarse aggregate such as rock) may be as given herein with respect to Table A1 and Table A2, such as at least 1000 psi and less than 10,000 psi, at least 2000 psi and less than 9000 psi, at least 2000 psi and less than 8,000, at least 3000 psi and less than 7,000 psi at 1, 7, 14, or 28 days. In some embodiments, the porosity of formed building materials comprising sequestered-CO₂ component and aggregate (e.g., fine aggregate such as sand and/or coarse aggregate such as rock) may be as given herein with respect to Table A1 and Table A2, such as at least 20% and less than 70%, such as at least 30% and less than 60%.

As described herein, the cement component in compositions for producing formed building materials may be entirely sequestered-CO₂ component; however, the cement component in compositions for producing the formed building materials described herein may further comprise conventional hydraulic cement (e.g., OPC). Conventional hydraulic cements are not the sequestered-CO₂ component or derived from precipitation material as described herein. Compositions for producing formed building materials that contain a conventional cement component, may contain one or more of the following hydraulic cement compositions: Portland cement blends such as Portland blast furnace cement; Portland fly ash cement; Portland pozzolan cement; Portland silica fume cement; masonry cements comprising limestone, hydrated lime, air entrainers, retarders, waterproofers, and coloring agents; plastic cements, stucco cements; expansive cements; white blended cements; colored cements; very finely ground cements; and non-Portland cements such as pozzolan-lime cements; slag-lime cements; supersulfated cements; calcium sulfoaluminate cements; natural cements; geopolymer cements. Of interest in certain embodiments as the conventional hydraulic cement is Portland cement. The Portland cement component may be any convenient Portland cement. As is known in the art, Portland cements are powder compositions produced by grinding Portland cement clinker (more than 90%), a limited amount of calcium sulfate which controls the set time, and up to 5% minor constituents (as allowed by various standards). As defined by the European Standard EN197.1, Portland cement clinker is a hydraulic material which shall consist of at least two-thirds by mass of calcium silicates (3CaO.SiO₂ and 2CaO.SiO₂), the remainder consisting of aluminum- and iron-containing clinker phases and other compounds. The ratio of CaO to SiO₂ shall not be less than 2.0. The magnesium content (MgO) shall not exceed 5.0% by mass. In certain embodiments, the Portland cement constituent may be any Portland cement that satisfies the ASTM Standards and Specifications of C150 (Types I-VIII) of the American Society for Testing of Materials (ASTM C50-Standard Specification for Portland Cement). ASTM C150 covers eight types of Portland cement, each possessing different properties, and used specifically for those properties.

Various cement blends comprising the sequestered-CO₂ component may be used, and each cement blend may contribute to large reductions in carbon footprint for formed building materials described herein. The sequestered-CO₂ component may be employed as, for example, a partial cement substitute for ordinary Portland cement, optionally in conjunction with fly ash, slag, and/or metakaolin, to produce a cement blend for formed building materials with small, neutral (i.e., approximately zero), or negative carbon footprint. As provided herein, such sequestered-CO₂ component may comprise calcium carbonate polymorphs such as amorphous calcium carbonate, vaterite, aragonite, and/or calcite in the proportions further described herein. In some embodiments, a cement blend such as that in Table A2 may comprise a conventional cement and sequestered-CO₂ component, and may have at least 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 99.9% by weight of sequestered-CO₂ component, the remainder being primarily conventional cement (e.g., OPC), optionally in conjunction with fine and/or coarse aggregate, and further optionally in conjunction with supplementary cementitious materials such fly ash, slag, and/or metakaolin. In some embodiments, a cement blend such as that in Table A2 may comprise a conventional cement and sequestered-CO₂ component, and may have less than 99.9%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 89%, 88%, 87%, 86%, 85%, 84%, 83%, 82%, 81%, 80%, 79%, 78%, 77%, 76%, 75%, 74%, 73%, 72%, 71%, 70%, 69%, 68%, 67%, 66%, 65%, 64%, 63%, 62%, 61%, 60%, 59%, 58%, 57%, 56%, 55%, 54%, 53%, 52%, 51%, 50%, 49%, 48%, 47%, 46%, 45%, 44%, 43%, 42%, 41%, 40%, 39%, 38%, 37%, 36%, 35%, 34%, 33%, 32%, 31%, 30%, 29%, 28%, 27%, 26%, 25%, 24%, 23%, 22%, 21%, 20%, 19%, 18%, 17%, 16%, 15%, 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, or 1% by weight of sequestered-CO₂ component, the remainder being primarily conventional cement (e.g., OPC), optionally in conjunction with fine and/or coarse aggregate, and further optionally in conjunction with supplementary cementitious materials such fly ash, slag, and/or metakaolin. Combinations of the foregoing are also useful for describing cement blends comprising sequestered-CO₂ component and a conventional cement. For example, a cement blend comprising sequestered-CO₂ component and conventional cement, may be at least 5% and less than 30% by weight sequestered-CO₂ component, the remainder being primarily cement (e.g., OPC), optionally in conjunction with fine and/or coarse aggregate, and further optionally in conjunction with supplementary cementitious materials such fly ash, slag, and/or metakaolin. Without being bound by theory, it is thought that the addition of sequestered-CO₂ component comprising carbonates provides sites for nucleation, causing early strength gains in formed building materials as shown in FIG. 13. It is further thought that analogs of calcium aluminosulfate hydrates are formed in which the sulfates are replaced by carbonates in the precipitation material. Because carbonates mostly interact with Al- (or Fe-) containing phases to form carboaluminates hydrates, and since Al₂O₃ content can be low in cement (e.g., OPC), slag may be used (as described herein) to increase Al₂O₃ content when producing formed building materials described herein. Table A2 describes the composition of formed building materials comprising such components (e.g., cement component, aggregate, supplementary cementitious material (“SCM”)):

TABLE A2 Compositions for formed building materials Cement Component Cement Blend (Sequestered-CO₂ Aggregate Component and Fine Coarse SCM Compo- Conventional Aggre- Aggre- Fly Meta- sitions Cement) gate gate Ash Slag kaolin 32 X 33 X X 34 X X X 35 X X X X 36 X X X X X 37 X X X X X X 38 X X X X X 39 X X X X X 40 X X X X 41 X X 42 X X X 43 X X X X 44 X X X X X 45 X X X 46 X X X X 47 X X X X X 48 X X X X 49 X X X X 50 X X X 51 X X X 52 X X X X 53 X X X X X 54 X X X X 55 X X X X 56 X X X 57 X X 58 X X X 59 X X X X 60 X X X 61 X X X 62 X X The fine aggregate described in the Table A2 may be conventional fine aggregate such as sand or aggregate comprising a sequestered-CO₂ component as described in U.S. patent application Ser. No. 12/475,378, filed 29 May 2009, which application is incorporated herein by reference in its entirety. The coarse aggregate described in the Table A2 may be conventional coarse aggregate such as gravel, crushed stone, slag, recycled concrete, geosynthetic aggregate, glass, or aggregate comprising a sequestered-CO₂ component as described in U.S. patent application Ser. No. 12/475,378. Fly ash, slag, and/or metakaolin are considered supplementary cementitious materials to a skilled person the art.

Porosity of formed building materials produced from the compositions of Table A2, in which the cement component is a cement blend comprising a conventional cement and sequestered-CO₂ component, may be, in some embodiments, at least 5%, 10%, 15%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 75%, 80%, 85%, 90%, or 95%. In some embodiments, the porosity of formed building materials of Table A2 may be less than 95%, 90%, 85%, 80%, 75%, 70%, 69%, 68%, 67%, 66%, 65%, 64%, 63%, 62%, 61%, 60%, 59%, 58%, 57%, 56%, 55%, 54%, 53%, 52%, 51%, 50%, 49%, 48%, 47%, 46%, 45%, 44%, 43%, 42%, 41%, 40%, 39%, 38%, 37%, 36%, 35%, 34%, 33%, 32%, 31%, 30%, 29%, 28%, 27%, 26%, 25%, 24%, 23%, 22%, 21%, 20%, 15%, 10%, or 5%. Combinations of the foregoing porosities are also useful for describing the porosity of formed building materials of Table A2. For example, the porosity of formed building materials may be, in some embodiments, at least 20% and less than 70%, such as at least 30% and less than 60%.

In some embodiments, for example, a cement blend comprising conventional cement and sequestered-CO₂ component, may be at least 10% and less than 90% by weight, such as at least 30% and less than 70% by weight, including at least 40 and less than 60% by weight, etc. sequestered-CO₂ component, the remainder being primarily cement (e.g., OPC), optionally in conjunction with fly ash, slag, and/or metakaolin. In some embodiments, the sequestered-CO₂ component may be employed as, for example, a complete (i.e., 100%) cement substitute for ordinary Portland cement (or any other cement), optionally in conjunction with fly ash, slag, and/or metakaolin, to produce a cement blend for a formed building material with a small, neutral (i.e., approximately zero), or negative carbon footprint.

Compressive strengths of formed building materials produced from the compositions of Table A2, in which the cement component may be sequestered-CO₂ component in combination with one or more additional cement component (e.g., OPC), may be, in some embodiments, at least at least 500 psi, 750 psi, 1000 psi, 1250 psi, 1500 psi, 1750 psi, 2000 psi, 2250 psi, 2500 psi, 2750 psi, 3000 psi, 3250 psi, 3500 psi, 3750 psi, 4000 psi, 4250 psi, 4500 psi, 4750 psi, 5000 psi, 5250 psi, 5500 psi, 5750 psi, 6000 psi, 6250 psi, 6500 psi, 6750 psi, 7000 psi, 7250 psi, 7500 psi, 7750 psi, 8000 psi, 8250 psi, 8500 psi, 8750 psi, 9000 psi, 9,250 psi, 9,500 psi, 9,750 psi, or 10,000 psi at in 1, 7, 14, or 28 days. Such formed building materials may have a compressive strength of less than 10,000 psi, 9750 psi, 9500 psi, 9250 psi, 9000 psi, 8750 psi, 8500 psi, 8250 psi, 8000 psi, 7750 psi, 7500 psi, 7250 psi, 7000 psi, 6750 psi, 6500 psi, 6250 psi, 6000 psi, 5750 psi, 5500 psi, 5250 psi, 5000 psi, 4750 psi, 45000 psi, 4250 psi, 4000 psi, 3750 psi, 3500 psi, 3250 psi, 3000 psi, 2750 psi, 2500 psi, 2250 psi, 2000 psi, 1750 psi, 1500 psi, 1250 psi, 1000 psi, 750 psi, or 500 psi at 1, 7, 14, or 28 days. Combinations of the foregoing compressive strengths are also useful for describing compressive strengths for formed building materials of Table A2, in which the cement component is a cement blend. For example, compressive strengths of such formed building materials may have a compressive strength of at least 2000 psi and less than 6000 psi at 1, 7, 14, or 28 days. As such, formed building materials with a small, neutral, or negative carbon footprint are suitable for use in any applications in which formed building materials are used.

The cement component, whether sequestered-CO₂ component alone or a cement blend comprising conventional cement and sequestered-CO₂ component, may form a binary mixture with up to 80% supplementary cementitious material by weight, the remainder of material being the cement component (excluding aggregate and water); ternary mixtures comprising at least two supplementary cementitious materials, quaternary mixtures comprising as least three supplementary cementitious materials, etc. may also have up to 80% supplementary cementitious materials by weight, the remainder of material being the cement component (e.g., sequestered-CO₂ component alone or a cement blend comprising conventional cement and the sequestered-CO₂ component). Table A1 and Table A2 provide further information on how supplementary cementitious materials may be combined with cement components to produce formed building materials comprising such supplementary cementitious materials. Unless indicated otherwise, other additives (e.g., GLENIUM® 7500) that may be used in compositions for producing formed building materials are assumed to be negligible with respect to the cement component (e.g., ordinary Portland cement (“OPC”); sequestered-CO₂ component; cement blends comprising conventional cement and sequestered-CO₂ component) and the supplementary cementitious materials. In some embodiments, a binary mixture comprising an supplementary cementitious materials and the cement component, whether sequestered-CO₂ component alone or a cement blend comprising conventional cement and sequestered-CO₂ component, may have at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, or 80% by weight of supplementary cementitious materials (e.g., fly ash, slag, and/or metakaolin as in Table A1 or Table A2), the remainder being primarily the cement component. In some embodiments, a binary mixture comprising an supplementary cementitious materials and the cement component, whether sequestered-CO₂ component alone or a cement blend comprising conventional cement and sequestered-CO₂ component, may have less than 80, 79, 78, 77, 76, 75, 74, 73, 72, 71, 70, 69, 68, 67, 66, 65, 64, 63, 62, 61, 60, 59, 58, 57, 56, 55, 54, 53, 52, 51, 50, 49, 48, 47, 46, 45, 44, 43, 42, 41, 40, 39, 38, 37, 36, 35, 34, 33, 32, 31, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1% by weight of supplementary cementitious materials (e.g., fly ash, slag, and/or metakaolin as in Table A1 or Table A2), the remainder being primarily the cement component. Combinations of the foregoing are also possible. For example, in some embodiments, a binary mixture comprising the cement component and an supplementary cementitious materials (e.g., fly ash, slag, and/or metakaolin as in Table A1 or Table A2), may have at least 1% and less than 60%, at least 5% and less than 30%, at least 10% and less than 30% by weight of supplementary cementitious materials, the remainder being primarily the cement component. In some embodiments, a binary mixture is provided for formed building materials comprising 90% cement component (e.g., 70% OPC and 10% sequestered-CO₂ component) and 20% fly ash. And, optionally, in such embodiments, the resulting formed building material may have a compressive strength of at least 4000 psi in 7 days and/or a compressive strength of at least 6000 psi in 28 days. In terms of shrinkage, the formed building materials in such embodiments may have a shrinkage less than −0.015% at 7 days, −0.020% at 14 days, −0.025% at 21 days, and/or −0.030% at 28 days (SEAONC Method). In some embodiments, a binary mixture is provided for formed building materials comprising 85% cement component (e.g., 70% OPC and 15% sequestered-CO₂ component) and 15% fly ash. And, optionally, in such embodiments, the resulting formed building material may have a compressive strength of at least 4000 psi in 7 days and/or a compressive strength of at least 6000 psi in 28 days. In terms of shrinkage, the formed building materials in such embodiments may have a shrinkage less than −0.015% at 7 days, 0.020% at 14 days, −0.025% at 21 days, and/or −0.030% at 28 days (SEAONC Method). In some embodiments, a binary mixture is provided for formed building materials comprising 85% cement component (e.g., 70% OPC and 15% sequestered-CO₂ component) and 15% slag. In some embodiments, a binary mixture is provided for formed building materials comprising 60% cement component (e.g., 40% OPC and 20% sequestered-CO₂ component) and 40% slag. And, optionally, in such embodiments, the resulting formed building material may have a compressive strength of at least 6000 psi in 7 days and/or a compressive strength of at least 8000 psi in 28 days. In terms of shrinkage, the formed building materials in such embodiments may have a shrinkage less than −0.015% at 7 days, −0.020% at 14 days, −0.025% at 21 days, and/or −0.030% at 28 days (SEAONC Method). In some embodiments, a binary mixture is provided for formed building materials comprising 50% cement component (e.g., 30% OPC and 20% sequestered-CO₂ component) and 50% slag. And, optionally, in such embodiments, the resulting formed building material may have a compressive strength of at least 6000 psi in 7 days and/or a compressive strength of at least 8000 psi in 28 days. In terms of shrinkage, the formed building materials in such embodiments may have a shrinkage less than −0.015% at 7 days, −0.020% at 14 days, −0.025% at 21 days, and/or −0.030% at 28 days (SEAONC Method). In some embodiments, a binary mixture is provided for formed building materials comprising 40% cement component (e.g., 20% OPC and 20% sequestered-CO₂ component) and 60% slag. And, optionally, in such embodiments, the resulting formed building material may have a compressive strength of at least 5000 psi in 7 days and/or a compressive strength of at least 6000 psi in 28 days. In terms of shrinkage, the formed building materials in such embodiments may have a shrinkage less than −0.015% at 7 days, 0.020% at 14 days, −0.025% at 21 days, and/or −0.030% at 28 days (SEAONC Method).

Ternary mixtures (as well as quaternary mixtures, quinary mixtures, etc.) are best described with respect to the cement component, whether sequestered-CO₂ component alone or a cement blend comprising conventional cement and sequestered-CO₂ component, in combination with a bulk supplementary cementitious material, which bulk supplementary cementitious material includes, for example, one of fly ash, slag, or metakaolin in excess of any other supplementary cementitious material. In such ternary mixtures (as well as quaternary mixtures, quinary mixtures, etc.), the bulk supplementary cementitious material (e.g., fly ash, slag, or metakaolin) may be at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, or 80% by weight of the combination of cement component and the bulk supplementary cementitious material (e.g., fly ash, slag, and/or metakaolin as in Table A1 or Table A2). In some embodiments, the bulk supplementary cementitious material (e.g., fly ash, slag, or metakaolin) may be less than 80, 79, 78, 77, 76, 75, 74, 73, 72, 71, 70, 69, 68, 67, 66, 65, 64, 63, 62, 61, 60, 59, 58, 57, 56, 55, 54, 53, 52, 51, 50, 49, 48, 47, 46, 45, 44, 43, 42, 41, 40, 39, 38, 37, 36, 35, 34, 33, 32, 31, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1% by weight of the combination of cement component and the bulk supplementary cementitious material (e.g., fly ash, slag, and/or metakaolin as in Table A1 or Table A2). Combinations of the foregoing are also possible. For example, in some embodiments, the bulk supplementary cementitious material, may be at least 1% and less than 60%, at least 5% and less than 30%, at least 10% and less than 30% by weight of the combination of cement component and the bulk supplementary cementitious material (e.g., fly ash, slag, and/or metakaolin as in Table A1 or Table A2).

Further with respect to such ternary mixtures (as well as quaternary mixtures, quinary mixtures, etc.), in some embodiments, the combination of bulk supplementary cementitious material and cement component, whether the cement component is sequestered-CO₂ component alone or a cement blend comprising conventional cement and sequestered-CO₂ component, may comprise at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, or 79% by weight of the ternary mixture, the remainder being one or more additional supplementary cementitious materials such as fly ash, slag, and/or metakaolin (e.g., supplementary cementitious materials as in Table A1 or Table A2). In some embodiments, the combination of bulk supplementary cementitious material and cement component, whether the cement component is sequestered-CO₂ component alone or a cement blend comprising conventional cement and sequestered-CO₂ component, may comprise less than 79, 78, 77, 76, 75, 74, 73, 72, 71, 70, 69, 68, 67, 66, 65, 64, 63, 62, 61, 60, 59, 58, 57, 56, 55, 54, 53, 52, 51, 50, 49, 48, 47, 46, 45, 44, 43, 42, 41, 40, 39, 38, 37, 36, 35, 34, 33, 32, 31, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1% by weight of the ternary mixture, the remainder being one or more additional supplementary cementitious materials such as fly ash, slag, and/or metakaolin (e.g., supplementary cementitious materials as in Table A1 or Table A2). In some embodiments, the remainder of additional supplementary cementitious material(s) may comprise at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, or 79% fly ash, optionally in combination with an amount (in weight percent) of slag and/or metakaolin as described herein (e.g., Table A1 or Table A2). In some embodiments, the remainder of additional supplementary cementitious material(s) may comprise less than 79, 78, 77, 76, 75, 74, 73, 72, 71, 70, 69, 68, 67, 66, 65, 64, 63, 62, 61, 60, 59, 58, 57, 56, 55, 54, 53, 52, 51, 50, 49, 48, 47, 46, 45, 44, 43, 42, 41, 40, 39, 38, 37, 36, 35, 34, 33, 32, 31, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1% fly ash, optionally in combination with an amount (in weight percent) of slag and/or metakaolin as described herein (e.g., Table A1 or Table A2). In some embodiments, the remainder of additional supplementary cementitious material(s) may comprise at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, or 79% slag, optionally in combination with an amount (in weight percent) of fly ash and/or metakaolin as described herein (e.g., Table A1 or Table A2). In some embodiments, the remainder of additional supplementary cementitious material(s) may comprise less than 79, 78, 77, 76, 75, 74, 73, 72, 71, 70, 69, 68, 67, 66, 65, 64, 63, 62, 61, 60, 59, 58, 57, 56, 55, 54, 53, 52, 51, 50, 49, 48, 47, 46, 45, 44, 43, 42, 41, 40, 39, 38, 37, 36, 35, 34, 33, 32, 31, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1% slag, optionally in combination with an amount (in weight percent) of fly ash and/or metakaolin as described herein (e.g., Table A1 or Table A2). In some embodiments, the remainder of additional supplementary cementitious material(s) may comprise at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, or 79% metakaolin, optionally in combination with an amount (in weight percent) of slag and/or fly ash as described herein (e.g., Table A1 or Table A2). In some embodiments, the remainder of additional supplementary cementitious material(s) may comprise less than 79, 78, 77, 76, 75, 74, 73, 72, 71, 70, 69, 68, 67, 66, 65, 64, 63, 62, 61, 60, 59, 58, 57, 56, 55, 54, 53, 52, 51, 50, 49, 48, 47, 46, 45, 44, 43, 42, 41, 40, 39, 38, 37, 36, 35, 34, 33, 32, 31, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1% metakaolin, optionally in combination with an amount (in weight percent) of slag and/or fly ash as described herein (e.g., Table A1 or Table A2).

In producing the formed building materials, an amount of the sequestered-CO₂ component may be combined with water and other additional components, which may include, but are not limited to clay, shale, soft slate, calcium silicate, quarried stone, Portland cement, fly ash, slag cement, aggregate (e.g., blast furnace slag, bottom ash, gravel, limestone, granite, sand, etc.), silica fume, pozzolans, reinforcing materials, such as steal or polymeric structures, etc., and then shaped into the final desired building material structure. Fabrication protocols may include extrusion, with or without heat of dry powder, powder made into a paste with fresh water, slurry from reactor, etc. Also of interest are fabrication protocols that include the use of rollers, e.g., to make a sheet, or rollers with impressions to make shapes. In addition, compression molding fabrication protocols may find use, e.g., dry molding, adding some water and molding, followed in some instances with sintering, etc. Fabrication protocols may include adding water (with or without additional binders such as plastics, Portland cement, etc.) to a dry composition of sequestered-CO₂ component (e.g., precipitation material comprising carbonates, bicarbonates, or a combination thereof), and casting the articles. Certain protocols may include heating the material to produce a formed building material via water turning into internal steam. Also of interest are protocols where amounts of precipitation material are maintained in an outdoor location so that they get rained on, recycling fresh water through the material to dissolve the metastable form and reprecipitate as a stable form, letting it stand in water for a time at room or elevated temp, and then producing the formed material from the set product.

Material that is not used to produce formed building materials may be used as amorphous building material. As with formed building materials, a substantial carbon reduction may result from using amorphous building material. For example, a substantial carbon reduction may result from combining both the cement credit (i.e., the CO₂ avoided) from offsetting the use of Portland cement and the quantity of sequestered carbon from fossil point sources. Each ton of material comprising a sequestered-CO₂ component (e.g., component comprising carbonates, bicarbonates, or combinations thereof) may result in a CO₂ reduction of up to 1 ton or more, such as 1.2 tons or more, including 1.6 tons or more, for example 2 tons or more of CO₂. Various binary, ternary, quaternary, etc. blends comprising a sequestered-CO₂ component (e.g., component comprising carbonates, bicarbonate, or a combination thereof) may result in such reductions. Whether for a formed or amorphous building material, sequestered-CO₂ component may be employed as, for example, a cement substitute (or a partial cement substitute), in conjunction with fly ash, slag, and/or Portland cement to produce a blended cement with a low, neutral (i.e., zero), or negative carbon footprint. Such blended cement may also have a compressive strength at or above 1,000 psi, including at or above 2,000 psi, e.g., at or above, 2,500 psi in 28 days or less, e.g., 14 days or less. As such, a blended cement with a low, neutral, or negative carbon footprint may produce quality concrete suitable for use in concrete pavement applications.

Also provided herein are low, neutral, and negative carbon footprint concrete mixes for use as an amorphous building material or in a formed building material. In some embodiments, low, neutral, or negative carbon footprint concrete mixes comprise a blended cement (e.g., supplementary cementitious material comprising a sequestered-CO₂ component comprising carbonates, bicarbonates, or a combination thereof in conjunction with fly ash, slag, and/or Portland cement) and an aggregate (e.g., the aggregate being coarse aggregate; fine aggregate such as sand; etc.), which aggregate may be prepared from a sequestered-CO₂ component in accordance with U.S. patent application Ser. No. 12/475,378, filed 29 May 2009, which is incorporated herein by reference. Such compositions may include, for example, a fine aggregate (e.g., sand) that has a sequestered CO₂ content of approximately 20% or more, e.g., 35% or more, including 50% or more. In some embodiments, the compressive strength of the concrete low, neutral, or negative carbon concrete is 2,500 psi or more at 28 days, e.g., 3000 psi or more, including 4,000 psi at 28 days. Some embodiments provide a carbon negative footprint concrete, which exhibits compressive strengths of 4,000 psi at 28 days. Equal early strengths (i.e., at 28 days) allow for the use of low, neutral, or negative carbon footprint concrete without negatively affecting construction schedules.

Embodiments achieve a low, neutral, or negative carbon footprint concrete, which not only meets the strength and early strength criteria (above), but also finishes like normal concrete. Blended cement-concrete compositions behave in a fashion similar to conventional Portland cement-concrete compositions enabling the blended cement-concrete compositions to be used in similar places and for similar functions. In some embodiments, blended cement-concrete compositions may be used in formed building materials. In some embodiments, blended cement-concrete compositions may be used for amorphous building material. For example, blended cement-concrete compositions may be placed into parking areas (e.g. a 5,000 square foot parking lot). Blended cement-concrete compositions, due to the higher albedo of such compositions, reduce carbon emissions via reduced lighting demands. This reduction of carbon emissions may occur over the lifetime of the blended cement-concrete compositions. For example, albedo and luminance measurements of low, neutral, or negative carbon footprint concrete parking areas compared to asphalt parking areas may be used to determine the difference in lighting needed and, thus, the level of carbon reduction that is possible due to the use of higher albedo concrete compositions. Albedo tests of such compositions demonstrate urban heat island reduction abilities, e.g., by 2-fold or more, 5-fold or more, 10-fold or more, 20-fold or more.

Utility

Building materials find use in a variety of different applications. Specific structures in which the building materials find use include, but are not limited to: buildings (both commercial and residential), infrastructure, e.g., walls, sound barriers, pipes, etc., and other man-made structures.

The subject methods and systems find use in CO₂ sequestration, particularly via sequestration in the built environment. Sequestering CO₂ comprises removal or segregation of CO₂ from the gaseous stream, such as a gaseous waste stream, and fixating it into a stable non-gaseous form so that the CO₂ cannot escape into the atmosphere. CO₂ sequestration comprises the placement of CO₂ into a storage stable form, e.g., a component of the built environment, such as a building, road, dam, levee, foundation, etc. As such, sequestering of CO₂ results in prevention of CO₂ gas from entering the atmosphere and long-term storage of CO₂ in a manner that CO₂ does not become part of the atmosphere. By storage stable form is meant a form of matter that can be stored above ground or underwater under exposed conditions (i.e., open to the atmosphere, underwater environment, etc.) without significant, if any, degradation for extended durations, e.g., 1 year or longer, 5 years or longer, 10 years or longer, 25 years or longer, 50 years or longer, 100 years or longer, assuming the building material of interest is maintained in its normal environment of its intended use.

The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description, and are not intended to limit the scope of what the inventors regard as their invention nor are they intended to represent that the experiments below are all or the only experiments performed. Efforts have been made to ensure accuracy with respect to numbers used (e.g. amounts, temperature, etc.) but some experimental errors and deviations should be accounted for.

EXAMPLES

Materials produced in accordance with this disclosure used one or more of the following analytical instruments and/or methods for characterization.

Coulometry:

Liquid and solid carbon containing samples were acidified with 2.0 N perchloric acid (HClO₄) to evolve carbon dioxide gas into a carrier gas stream, and subsequently scrubbed with 3% w/v silver nitrate at pH 3.0 to remove any evolved sulfur gasses prior to analysis by an inorganic carbon coulometer (UIC Inc, model CM5015). Samples of cement, fly ash, and seawater are heated after addition of perchloric acid with a heated block to aid digestion of the sample.

Brunauer-Emmett-Teller (“BET”) Specific Surface Area:

Specific surface area (SSA) measurement was by surface absorption with dinitrogen (BET method). SSA of dry samples was measured with a Micromeritics Tristar™ II 3020 Specific Surface Area and Porosity Analyzer after preparing the sample with a Flowprep™ 060 sample degas system. Briefly, sample preparation involved degassing approximately 1.0 g of dry sample at an elevated temperature while exposed to a stream of dinitrogen gas to remove residual water vapor and other adsorbants from the sample surfaces. The purge gas in the sample holder was subsequently evacuated and the sample cooled before being exposed to dinitrogen gas at a series of increasing pressures (related to adsorption film thickness). After the surface was blanketed, the dinitrogen was released from the surface of the particles by systematic reduction of the pressure in the sample holder. The desorbed gas was measured and translated to a total surface area measurement.

Particle Size Analysis (“PSA”):

Particle size analysis and distribution were measured using static light scattering. Dry particles were suspended in isopropyl alcohol and analyzed using a Horiba Particle Size Distribution Analyzer (Model LA-950V2) in dual wavelength/laser configuration. Mie scattering theory was used to calculate the population of particles as a function of size fraction, from 0.1 mm to 1000 mm.

Powder X-Ray Diffraction (“XRD”):

Powder X-ray diffraction was undertaken with a Rigaku Miniflex™ (Rigaku) to identify crystalline phases and estimate mass fraction of different identifiable sample phases. Dry, solid samples were hand-ground to a fine powder and loaded on sample holders. The X-ray source was a copper anode (Cu ka), powered at 30 kV and 15 mA. The X-ray scan was run over 5-90°2θ, at a scan rate of 2°2θ per min, and a step size of 0.01°2θ per step. The X-ray diffraction profile was analyzed by Rietveld refinement using the X-ray diffraction pattern analysis software Jade™ (version 9, Materials Data Inc. (MDI)).

Fourier Transform Infrared (“FT-IR”) Spectroscopy:

FT-IR analyses were performed on a Nicolet 380 equipped with the Smart Diffuse Reflectance module. All samples were weighed to 3.5±0.5 mg and hand ground with 0.5 g KBr and subsequently pressed and leveled before being inserted into the FTIR for a 5-minute nitrogen purge. Spectra were recorded in the range 400-4000 cm⁻¹.

Scanning Electron Microscopy (“SEM”):

SEM was performed using a Hitachi TM-1000 tungsten filament tabletop microscope using a fixed acceleration voltage of 15 kV at a working pressure of 30-65 Pa, and a single BSE semiconductor detector. Solid samples were fixed to the stage using a carbon-based adhesive; wet samples were vacuum dried to a graphite stage prior to analysis. EDS analysis was performed using an Oxford Instruments SwiftED-TM system, the sensor for which has a detection range of 11Na-92U with an energy resolution of 165 eV.

Alternatively, SEM was performed using a Hitachi SU-6600 field emission microscope capable of operation at accelerating voltages ranging from 0.5-30 kV at working pressures ranging from 10-8-300 Pa. Available detectors include a SE, BSE, and ESED. EDX analysis utilized an Oxford Instruments INCA Energy SEM 350 Energy Dispersive Microanalysis system with a INCA X-ACT Analytical Drift Detector, having a detection range of Be—Pu and a resolution of 129 eV. Sample preparation involves fixation to a stage by means of either a carbon-based adhesive or silver paint. Non-conductive samples are coated with a thin layer of either gold or carbon prior to analysis.

Chloride:

Chloride concentrations were determined with Chloride QuanTab® Test Strips (Product No. 2751340), having a testing range between 300-6000 mg chloride per liter solution measured in 100-200 ppm increments.

X-Ray Fluorescence (“XRF”):

XRF analyses of solid powder samples were performed using a Thermo Scientific ARL QUANT'X Energy-Dispersive XRF spectrometer, equipped with a silver anode X-ray source and a Peltier cooled Si(Li) X-ray detector. The samples were pressed into 31 mm pellets using an aluminum sample cup. For each sample, three different spectra were gathered, each tailored for analysis of specific elements: the first using no X-ray filter at 4 kV, the second using a thin silver filter at 18 kV, and the third using a thick silver filter at 30 kV, all under vacuum conditions. Spectra were analyzed using WinTrace software, using a Fundamental Parameters analysis method attained from calibration with certified standard materials.

Thermogravimetric Analysis (“TGA”):

TGA analyses of solid powder samples were performed with a TA Instruments SDT Q600 with simultaneous TGA/DSC (Differential Scanning calorimetry). Samples, in an alumina crucible, were placed into a furnace that was heated from room temperature to 1000° C. at a constant ramp rate of 20° C. per minute. The weight loss profile over temperature was analyzed using Universal Analysis software.

Inductively Coupled Plasma Optical Emission Spectrometry (“ICP-OES”):

ICP-OES analyses of typical acidified, liquid samples were performed using a Thermo ICAP 6500 equipped with a CETAC autosampler. iTEVA control software was used for data acquisition and analysis. Although the detection limit for this method has not been determined typical detection limits are in the ppm range. Samples that contain high concentrations of dissolved salts (Na, Ca, Mg) were analyzed using the ICAP 6500 equipped with an ESI SEA fast autosampler equipped with a chelation column for matrix elimination analyte preconcentration.

Example 1 Preparation of Precipitation Material for Use as Partial Cement Substitute in Concrete

900 gallons of seawater was pumped at approximately 20 gallons per minute into a 1000-gallon tank with a covered headspace. Open access ports open for agitation, instrumentation, tank entry, and reagent addition were located on the top of the tank. An array of gas spargers was located in the bottom for sparging a carbon dioxide/air mixture. Approximately 30% (v/v) of the gas mixture sparged through the reactor was carbon dioxide gas. The seawater was agitated with an overhead mixer as the gas was sparged into the tank at a total flow rate of 40-50 lpm. The initial seawater temperature ranged from 15 to 20° C.

An aqueous solution of 50% sodium hydroxide (w/w) was pumped into the agitated, sparging vessel to maintain a pH of approximately pH 9.0. An automatic controller to maintain the desired pH adjusted the flow rate of the sodium hydroxide.

After 12 kg of 50% sodium hydroxide was added to the agitated, sparging vessel, both the caustic addition and the carbon dioxide gas flow to the vessel were ceased. The air continued to be sparged into the vessel and agitation maintained until the gas lines were purged of carbon dioxide. The air sparging was then ceased, but agitation maintained to keep the slurry in suspension. The final slurry temperature ranged from 15 to 25° C.

The resultant slurry was pumped to another covered tank with a conical bottom and outlet port at the bottom. The slurry was allowed to settle overnight. The supernatant was decanted the next day, and the settled slurry vacuum filtered.

The filter cake was re-suspended in fresh water to generate a pump able slurry for spray drying. The slurry was spray dried and the product collected from the spray dryer product collection cyclone.

X-ray fluorescence (“XRF”) (Table 8) and coulometry (Table 9) data indicate that the precipitation material is mostly composed of calcium carbonate.

TABLE 8 XRF elemental analysis of precipitation material Na Mg Al Si S Cl K Ca Fe Weight 1.44 0.27 0.22 0.24 0.14 1.52 0.01 37.99 0.14 %

TABLE 9 Percent CO₂ content (coulometry) % CO₂ Weight % 40.85

X-ray diffraction (“XRD”) analysis (FIG. 2) of the precipitation material indicates the presence of aragonite (CaCO₃) as the major phase, and halite (NaCl) as a minor component.

Scanning electron microscope (SEM) images of the precipitation material at 1000× (left) and 4000× (right) are provided as well (FIG. 3).

Example 2 Formed Materials

A. Concrete Cylinder (or Post)

A concrete cylinder was made from a batch of concrete prepared with spray-dried precipitation material such as that described in Example 1. The precipitation material was used as a partial cement substitute of Portland cement, replacing 17% by mass of the Portland cement. The batch was mixed in a small mixing drum using the following mix weights:

Portland Cement 13.98 lbs Fly Ash 3.55 lbs Aragonite precipitate 3.70 lbs Water 9.4 lbs Sand 45.74 lbs Small coarse aggregate 8.58 lbs Medium coarse aggregate 51.46 lbs Large coarse aggregate 8.58 lbs

Cylinders measuring 4″×8″ were formed according to ASTM C31. Each cylinder was consolidated in two equal layers and tamped 25 times each layer with a ⅜″ rod. The cylinders were then finished with a concrete trowel and capped. The integrity of the cylinders allowed for cutting the cylinders into 0.75″-1.5″ thick sections, which sections were then polished on both sides.

B. Concrete Tile (Modified Dimensions)

A filter cake of precipitation material prepared as in Example 1 was spray dried to a moisture content of approximately 4%. The spray-dried material was then dry blended with ordinary type-V Portland cement in a 4:1 ratio (ordinary Portland cement: spray-dried precipitation material) to obtain a total cementitious mixture. The total cementitious mixture was combined with fine aggregate, coarse aggregate, and water to form a concrete mixture. The products were mixed together in a small concrete mixing drum. The amounts added were as follows: 48.4 lb total cementitious (9.7 lb carbonate aragonite, 38.7 lb type-V Portland cement), 24.2 lb tap water, 111 lb fine aggregate, and 136 lb coarse aggregate. The concrete mixture was removed from the mixing drum into a wheelbarrow. The concrete was then scooped from the wheelbarrow into forms of the tile. The tile dimensions were 609.6 mm×609.6 mm×88.9 mm, approximately three times thicker (i.e., “modified”) than tiles described hereinabove. The concrete was consolidated into the forms using a ⅝″ tamping rod to prevent bug-holes. The tile was screeded and smooth-trowel finished. The following day, forms were removed yielding a modified concrete tile.

C. Paver

This study is related to using a carbonate composition to make pavers. The carbonate composition was prepared by blending six batches of the carbonate compositions that were prepared using similar conditions and reagents. Carbonate compositions were prepared by mixing brine solution (containing 0.19M Ca in sea water) with alkaline solution (containing 0.5M NaOH, pH 10.8-11.2 and carbonate obtained by mixing CO₂ in NaOH solution) in a 15-gallon precipitation tank. The dewatering was carried out using Lamella and Andritz and the composition was spray dried. The slurry in the tank or the precipitator showed particle size analysis (PSA) of 4.2 μm at 2.4 std; and vaterite with trace amount of calcite. The slurry in Lamella showed PSA of 7 μm at 3.5 std; and vaterite with trace amount of calcite. The slurry in Andritz showed PSA of 3.7 μm at 2.6 std and detectable amount of calcite. The dried materials showed mean particle size 3.5 μm; BET 12 m2/g; 83% vaterite; and 17% calcite.

The blended carbonate composition, after treatment with water, was poured as a paver.

Some of the data related to composition containing 20% carbonate composition (as described above to be a blend of six compositions) and 80% OPC, is as provided below in Table 10.

TABLE 10 Data related to composition containing 20% carbonate composition. 20% carbonate composition + Property Method GU Spec. 80% OPC Flow ASTM C1437 110 +/− 5%  89% @ 0.49 Vicat set time, min ASTM C191 45-240  51 1 day compression, psi ASTM C109 N/A (1740 1940 (98%) for HE) 3 days compression, psi ASTM C109 1890 3150 (99%) 7 days compression, psi ASTM C109 2900 3940 (93%) Air content of mortar, % ASTM C185 Report Value   4%

D. Paver

This study is related to using a carbonate composition to make pavers. The carbonate composition was prepared by blending three batches of the carbonate compositions that were prepared using similar conditions and reagents.

Carbonate composition 1 was prepared by mixing brine solution (containing 0.17M Ca, 0.02M Mg (Mg as MgCl₂), and 0.01M SO₄ (Na₂SO₄ as sulfate source) in municipal water) with alkaline solution (containing 0.5M NaOH, pH 10.7-10.9 and carbonate obtained by mixing CO₂ in NaOH solution) in a 15-gallon precipitation tank with an inline mixer.

Carbonate composition 2 was prepared by mixing brine solution (containing 0.2M Ca, 0.01M Mg (Mg as MgCl₂), and 0.01M SO₄ (Na₂SO₄ as sulfate source) in municipal water) with alkaline solution (containing 0.5M NaOH, pH 10.7-10.9 and carbonate obtained by mixing CO₂ in NaOH solution) in a 15-gallon precipitation tank with an inline mixer.

Carbonate composition 3 was prepared by mixing brine solution (containing 0.2M Ca, 0.01M Mg (Mg as MgCl2), and 0.01M SO₄ (Na₂SO₄ as sulfate source) in municipal water) with alkaline solution (containing 0.5M NaOH, pH 10.7-10.9 and carbonate obtained by mixing CO₂ in NaOH solution) in a 15-gallon precipitation tank with an inline mixer.

The three carbonate compositions were blended together. The carbonate composition thus obtained, was mixed with OPC and slag such that the mix design was 40% OPC, 40% slag, and 20% carbonate composition. The blended composition, after treatment with water and aggregate, was poured in a paver mold and compressed. When ready, the pavers were removed from the molds and stored on racks to cure. Table 11 illustrates compressive strength of the Ordinary Portland cement alone and when mixed with the carbonate composition.

TABLE 11 Properties for paver mixes using ordinary Portland cement (OPC) mix alone and mixed with the carbonate composition. Paver mix with Paver mix blend of OPC with OPC and carbonate alone composition OPC 460 lb/yd³ 185 lb/yd³ carbonate composition 0 275 lb/yd³ water/cement ratio 0.39 0.36 1 day compressive strength 3210 psi 2410 psi 7 day compressive strength 6820 psi 8380 psi 28 day compressive 8550 psi 10,090 psi strength

E. Paver

This study is related to using a carbonate composition to make pavers. The carbonate composition was prepared using similar reagents and conditions as given in the foregoing examples. The carbonate composition (about 99% mono-dispersed vaterite; about 2.5 micron particle size), was mixed with OPC and slag (XRF: Al₂O₃ 11%, SiO₂ 30%, CaO 45%; BET 107 m²/g; PSA 8 μm; XRD: amorphous, anhydrite—CaSO₄) such that the mix design was 40% OPC, 40% slag, and 20% carbonate composition. The blended composition, after addition of aggregate, and treatment with water (water:cement ratio of 0.39), was poured in a paver mold and compressed. When ready, the pavers were removed from the molds and stored on racks. The pavers were cured without additional heat or humidity. XRD showed formation of monocarbonaluminate from addition of the carbonate composition. Table 12 provides the compressive strength of the pavers, tested in accordance with ASTM C140-8A, Section 7:

TABLE 12 Properties for pavers comprising 40% OPC, 40% slag, and 20% carbonate composition. Paver Area (in₂) Max load (lbs) Compressive Strength 1 33.92 327,000 9640 2 34.00 309,000 9090 3 34.02 343,000 10080 4 33.80 344,500 10190 5 31.73 265,500 8370 6 33.88 306,000 9030 7 33.71 312,000 9260 8 33.92 351,000 10350

All examples and conditional language recited herein are principally intended to aid the reader in understanding the principles and the concepts contributed by the inventors to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents and equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure. The scope of the invention, therefore, is not intended to be limited to the exemplary embodiments shown and described herein as such embodiments are provided by way of example only. Indeed, numerous variations, changes, and substitutions may now occur to those skilled in the art without departing from the invention. It is intended that the following claims define the scope of the invention and that methods and structures within the scope of these claims and their equivalents be covered thereby. 

1-24. (canceled)
 25. A lightweight masonry unit, comprising: at least 50% w/w sequestered-CO₂ component, wherein the sequestered-CO₂ component comprises metastable carbonate selected from the group consisting of vaterite, aragonite, and combination thereof, wherein the sequestered-CO₂ component has a δ¹³C less than −15%, and wherein the lightweight masonry unit has a porosity of at least 30%.
 26. The lightweight masonry unit of claim 25, wherein the masonry unit has a porosity of between 30-90%.
 27. The lightweight masonry unit of claim 25, wherein the masonry unit comprises between 50-99% w/w carbonate or combination of carbonate and bicarbonate.
 28. The lightweight masonry unit of claim 25, wherein the masonry unit is a tile.
 29. The lightweight masonry unit of claim 28, wherein the tile is a ceiling tile.
 30. The lightweight masonry unit of claim 28, wherein the tile has a flexural strength of between 0.5 to 7.5 MPa, compressive strength of between 5 to 75 MPa, or both.
 31. The lightweight masonry unit of claim 25, wherein the masonry unit is a block.
 32. The lightweight masonry unit of claim 31, wherein the block has a flexural strength of between 0.5 to 15 MPa, compressive strength of between 5-100 MPa, or both.
 33. The lightweight masonry unit of claim 25, wherein the masonry unit further comprises one or more additives selected from anti-desiccant, plasticizer, fibrous material, accelerator, set retarder, foaming agent, mildew resistance agent, fire resistance agent, and polyvinyl alcohol.
 34. The lightweight masonry unit of claim 25, wherein the masonry unit further comprises recycled material selected from fly ash, slag, cement kiln dust, and combinations thereof.
 35. The lightweight masonry unit of claim 25, wherein the masonry unit further comprises at least one additional component selected from clay, shale, soft slate, calcium silicate, quarried stone, Portland cement, metakaolin, cement, aggregate, silica fume, and pozzolan.
 36. A method for producing a masonry unit, comprising: a) processing a waste gas stream comprising carbon dioxide with a process water to produce a composition wherein the composition comprises a metastable carbonate comprising vaterite, wherein the vaterite has a δ¹³C less than −15%; b) producing a slurry mixture from the composition; and c) processing the slurry mixture to form a lightweight masonry unit wherein the masonry unit comprises at least 50% w/w aragonite and has a porosity of between 30-90%.
 37. The method of claim 36, comprising transforming the vaterite to aragonite when the lightweight masonry unit is formed.
 38. The method of claim 36, further comprising concentrating the composition to dryness to produce a dry composition.
 39. The method of claim 36, wherein the method further comprises adding one or more additives to the slurry mixture, wherein the one or more additives are selected from the group consisting of anti-desiccant, fibrous material, accelerator, set retarder, plasticizer, foaming agent, polyvinyl alcohol, fire resistance agent, and mildew resistance agent.
 40. The method of claim 36, wherein the method further comprises adding recycled material to the slurry mixture wherein the recycled material is selected from the group consisting of fly ash, slag, cement kiln dust, and combinations thereof.
 41. The method of claim 36, further comprising depositing the slurry mixture in a mold without backing material, or between two sheets of backing material, wherein the backing material comprises sheets of paper or fiberglass.
 42. The method of claim 36, wherein the method further comprises adding at least one additional component to the slurry mixture selected from clay, shale, soft slate, calcium silicate, quarried stone, Portland cement, metakaolin, cement, aggregate, silica fume, and pozzolan.
 43. The method of claim 36 wherein the lightweight masonry unit is tile.
 44. The method of claim 36 wherein the lightweight masonry unit is block. 